<p class="jove_content"> Die Autoren danken Ruth Zelkha, MS, für ihre großzügige Unterstützung bei der Bildgebung. Diese Arbeit wurde von Clinical Scientist Development Program Preis K12EY021475 zu ME unterstützt wurde, gewähren R01 EY024349-01A1 auf ARD, Kern Zuschuss EY01792 vom National Eye Institute, NIH, und eine uneingeschränkte Gewährung von Forschungs Erblindung zu verhindern. ARD ist der Empfänger eines Career Development Award von Forschung zur Verhütung Blindheit. </p>

<p class="jove_content"> Alle Verfahren an Tieren durchgeführt, mit der Association for Research in Vision and Ophthalmology Aussagen für Tierversuche in der Vision Forschung entsprechen. Vierzehn vier- bis sechs Monate alten männlichen / weiblichen C57BL / 6J-Wildtyp-Mäusen wurden verwendet: zehn Mäuse für die Schadensmodell und vier als Kontrolltiere (unwounded Cornea). </p><p class="jove_title"> 1. Vorbereitung der Tiere </p><ol><li> Anästhesieren eine Maus mit einer intraperitonealen Injektion von 100 mg / kg Ketamin und 5 mg / kg Xylazin-Mischung. Nach der Anästhesie wirksam geworden ist, eine Prise der Spitze der Narkose Tiefe zu bestätigen; sollte das Tier nicht reagieren. </li><li> Untersuchen Sie das Auge unter einer Spaltlampe vor der Durchführung der Experimente das Fehlen einer früheren Verletzung der Hornhaut zu überprüfen. </li><li> Flößen Sie einen Tropfen von 1% Tetracainhydrochlorid auf das Auge. Nach 60 bis 90 Sekunden, testen Sie die Kornealreflex das Fehlen der Empfindung zu bestätigen. Proparacain-Hydrochlorid 0,5% können stattdessen verwendet werden. </li><li> Wenn der Verlust der Hornhautgefühl istsicher, sanft einen Rückgang von 5% PVP-Jod auf das Auge platzieren und auf das Haar um das Auge. Wischen Sie den Abfall nach 1 min aus oder verteilen es auf dem Haar um die Augen, das Haar zu verhindern, mit der Werkzeugspitze stören. </li></ol><p class="jove_title"> 2. Abschleifen der Hornhautepithel </p><ol><li> Tragen OP-Handschuhe und ein Kleid. Bereiten Sie die erforderlichen Werkzeuge: ein steriles Rotationsbohrer und ein Paar sterile Pinzette. Für eine bessere Kontrolle, verwenden gebogen Pinzette. Legen Sie die Werkzeuge auf einem sterilen Blatt während des Verfahrens. </li><li> Unter Verwendung der gebogenen Pinzette, stabilisieren das Auge durch den Deckel von der Nasenseite greifen und das Auge sanft proptosing. Vermeiden Sie zu viel Druck. </li><li> Unter einem Operationsmikroskop, rasieren 360 ° um den Limbus-Bereich zweimal die sterile Rotationsbohrer verwenden. Gehen Sie rund um den Limbus mit einer Geschwindigkeit von 5 - 6 Sekunden pro Runde. <br /> HINWEIS: Der Grat einer festen Geschwindigkeit hat. Doch für sie sollte verschärft werden vollständig bei der etablierten Geschwindigkeit, die &quot;End-Mutter&quot; zu drehen. </li><li> Entfernen Sie das gesamte Hornhautepithel von Limbus mit dem rotierenden Grat zu Limbus. Für bessere Ergebnisse, wobei das Werkzeug in einer kreisförmigen Art und Weise bewegen und halten es etwas parallel zur Hornhautoberfläche mit der lateralen Seite seiner Spitze zu arbeiten. Achten Sie darauf, nicht das Stroma zu verletzen, indem nicht wieder Bürsten der Bereiche, in denen das Epithel bereits entfernt wurde. Wenden Sie keinen Druck auf das Auge. Reinigen Sie die Pinselspitze nach Bedarf. </li><li> Flößen Sie einen Tropfen steriler phosphatgepufferter Salzlösung auf der Hornhaut und wischen Sie alle freistehende Epithellagen mit einem weichen Reinigungstuch. </li><li> Rasur die verbleibende Epithel, sofern vorhanden. </li><li> Achten Sie auf die Maus Schwanz während der Operation. <br /> HINWEIS: Wenn eine Bewegung stattfindet, hat die Narkose Tiefe verblasst und weitere Injektion erforderlich ist. Ein Drittel bis zwei Drittel des primären injizierte Volumen sollte ausreichen. Überdosierung Sie nicht das Tier mit dem Betäubungsmittel Medikamente. </li><li> Sterilisieren Sie alle Werkzeuge, bevor sie auf einem anderen Auge mit. </li></ol><p class="jove_title"> 3. Bestätigen Sie die komplette Epithelial Removal </p><ol><li> Einen Tropfen von 1 mg / ml Fluorescein-Natrium auf die Hornhaut. Reinigen Sie die Hornhaut nach 30 Sekunden und untersuchen sie unter einem Mikroskop mit einem Blaufilter die vollständige Entfernung des Epithels zu überprüfen. <br /> HINWEIS: Die Hornhautbereiche mit Epithelfehler sind grün dargestellt. </li></ol><p class="jove_title"> 4. Post-Betrieb Pflege </p><ol><li> Legen Sie das Tier auf einer Heizdecke und halten Sie sie an einem sicheren Ort <em>(zB</em> in seinem Käfig) , während unter Rückgewinnung. Nicht eine unbewusste Tier in der Gesellschaft von bewußten halten. </li><li> Bewerben 1% Erythromycin Augensalbe. Dies wird auch Augentrockenheit verhindern. Weiterhin die Anwendung des Antibiotikums täglich für eine Woche. </li><li> Injizieren von 0,1 mg / kg subkutan Buprenorphin nach dem Eingriff und wieder nach 12 Stunden. Weiterhin die Injektion zweimal pro Tag für zwei Tage. </li><li> Beobachten Sie das Tier für 30 - 45 min, bis zur vollständigen Erholung von der Anästhesie. <br /> HINWEIS: Leichte Bewegung der Atemmuskulatur auf der ventralen Oberfläche zeigt Tier Wellness, während sie unter Genesung. </li></ol>

<ol>
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<p class='jove_content'>The authors declare that they have nothing to disclose.</p>

<p class="jove_content"> Dieser Artikel beschreibt eine reproduzierbare und relativ einfache Technik, ein Mausmodell von LSCD zu erstellen. Es gibt mehrere wichtige Aspekte dieses Modells, die erwähnenswert sind. Erstens, anders als Modelle , die <sup>11 Chemikalien, 12,</sup> beinhaltet die Schädigung in erster Linie das Oberflächenepithel (und Basalmembran) mit minimaler Beschädigung des darunterliegenden Hornhautstroma oder anderen intraokularen Strukturen. Somit gibt es nur begrenzte Entzündung und Vernarbung, von denen beide das Verfa...

<p class="jove_content"> Das Hornhautepithel erforderlich, um die Klarheit und die Integrität der Hornhaut aufrechtzuerhalten. Es wird ständig während des gesamten Lebens durch die epithelialen Stammzellen in Limbus-einer schmalen Zone an der Verbindungsstelle der Hornhaut und der Bindehaut Wohnsitz erneuert. Diese sich selbst erneuernden Limbusstammzellen spielen eine entscheidende Rolle in der Hornhautepithel regenerierend, beide normal und nach der Verletzung. Eine teilweise oder vollständige Verarmung dieser Stammzellen wird bei rezidivierenden Hornhauterosionen, Schmerzen, Hornhautnarben und Neovaskularisation, Aussehen von Becherzellen zur Folge haben, und wenn sie nicht behandelt, Hornhautblindheit links. Dieser Zustand wird als Limbusstammzellinsuffizienzen (LSCD) bekannt und können idiopathische sein; erblich; oder durch chemische oder thermische Verletzungen erworben, langfristige Tragen von Kontaktlinsen, und eine chronische Entzündung <sup>1-6.</sup> </p><p class="jove_content"> Forschung auf LSCD erfordert ein geeignetes Tiermodell, das nicht nur imitiert die Krankheit beim Menschen, sondern ist reproduzierbar und nachhaltig ist, mit dem mindestens eineBerg Verletzungen anderer Hornhaut- und Augenstrukturen. Dieses Modell ist notwendige Behandlungen zu beurteilen und die Krankheitsmechanismen auf molekularer und zellulärer Ebene zu klären. Wie zuvor <sup>1</sup> beschrieben, mit der Verwendung einer rotierenden Fräse, kann man leicht ein Mausmodell der LSCD entwickeln, die die oben genannten Vorteile und bleibt für mindestens drei Monaten aufweist. Das Ziel dieser Studie ist es, eine einfache, reproduzierbare und nachhaltige Mausmodell der LSCD zu präsentieren. </p><p class="jove_content"> Der sich drehende Grat ist ein handliches Werkzeug , das gleichmäßig das Epithel entfernt , ohne die zugrunde liegende <sup>1</sup> Stroma zu verletzen. Es wurde <sup>7, 8</sup> in Wundheilungsstudien zu induzieren zentralen Hornhauterosion eingesetzt. Die hiermit präsentierte Technik LSCD in einer Maus zu schaffen, hat nicht vor berichtet. Zuvor Verfahren eingeführt in einer weniger einheitlichen das Epithel mit einem stumpfen Spatel Ergebnis Abschaben verletzungs insbesondere am Limbus-und eine variable Phänotyp <sup>1, 9,</sup> mit Wiederherstellung of normalen Hornhautepithel <sup>1.</sup> Im Gegensatz zu dem stumpfen Schaber, entfernt der Rotationsbohrer des epithelialen Basalmembran sowie <sup>7, 8, 10.</sup> Andere berichteten Verfahren Stammzellen abzutrennen, umfassen die Verwendung von Chemikalien, wie Natriumhydroxid, n-Heptanol, und Benzalkoniumchlorid, die nicht nur unerwünschte Schädigung zugrunde liegenden Augenstrukturen induzieren kann, sondern auch zu erheblichen Entzündung und nachfolgende kornealen opacification führen kann oder epithelialen Plattenepithelmetaplasie <sup>15.11.</sup> Der rotierende Grat ist nicht mit dieser schweren Komplikationen verbunden. Chirurgisch den Limbus Epithel entfernt, <sup>10</sup> allein oder mit der Verwendung von <sup>Chemikalien, 11, 16,</sup> ist schwieriger zu führen und ist nicht die beste Option bei Tieren mit kleinen Augen und einem dünnen Limbus Epithelien (wie Mäuse). Darüber hinaus kann überraschenderweise limbectomy noch etwas von dem Limbus Epithel hinter <sup>10</sup> verlassen. </p><p class="jove_content"> Die unten beschriebene Technik wird in LSCD mit Neovaskularisierung eine Folged conjunctivalization, die die Darstellung der kompletten LSCD bei Patienten und dauert mindestens drei Monate <sup>1</sup> nachahmt. Es ist geeignet für diejenigen, die darauf abzielen LSCD oder Wundheilung Pathophysiologie, Immunologie und mögliche Behandlungen bei Mäusen zu untersuchen. Gegebenenfalls mit einigen Modifikationen kann dieses Verfahren bei Ratten oder Kaninchen <sup>10</sup> durchgeführt werden. Da der Rotationsbohrer effizient das Epithel entfernt, kann es im Zusammenhang mit Hornhautepithels Abrasion / Verwundung und in jeder Behandlung benötigt oder Molekularbiologie Studien in jeder Forschung genutzt werden. </p>

<table><tbody><tr><td>Rotating burr: AlgerBrush II rust ring remover&amp;nbsp;</td><td>Rumex International Co, Clearwater, FL</td><td>16-141</td><td>0.5 mm burr. Also available from other companies.</td></tr><tr><td>Surgical microscope</td><td>Wild Heerbrugg, Switzerland</td><td>Wild M691</td><td></td></tr><tr><td>Digital camera</td><td>Nikon, Thailand</td><td></td><td></td></tr><tr><td>Nikon FS-2 slit lamp</td><td>Nikon, Japan</td><td></td><td></td></tr><tr><td>Polyclonal anti-CK12 antibody</td><td>Santa Cruz Blotechnology, CA,</td><td>SC-17101</td><td>1:100 concentration</td></tr><tr><td>Monoclonal anti-CK8 antibody</td><td>TROMA-I-s, Iowa City, IA</td><td>AB_531826</td><td>1:50 concentration</td></tr></tbody></table>

a simple mechanical procedure to create limbal stem cell deficiency in mouse

<p class="jove_content"> Limbusstammzellinsuffizienzen (LSCD) ist ein Zustand der Fehlfunktion oder den Verlust von Limbus-epithelialen Stammzellen, wonach das Hornhautepithel mit Bindehaut ersetzt wird. Die Patienten leiden unter wiederkehrenden Hornhautdefekte, Schmerzen, Entzündung und Verlust des Sehvermögens. </p><p class="jove_content"> Zuvor wurde ein Mausmodell der LSCD beschrieben und im Vergleich zu zwei anderen Modellen. Das Ziel war, ein einheitliches Mausmodell der LSCD zu erzeugen, die beide ahmt den Phänotyp beim Menschen und lange genug dauert es möglich zu machen, um die Krankheit Pathophysiologie zu studieren und zu neuen Therapien zu bewerten. Hier wird die Technik näher beschrieben. </p><p class="jove_content"> Ein motorisiertes Werkzeug mit einem rotierenden Grat wurde entwickelt, um die Rostringe von der Hornhautoberfläche zu entfernen oder das Pterygium Bett bei Patienten zu glätten. Es ist eine geeignete Vorrichtung die gewünschte LSCD Modell zu erstellen. Es ist ein leicht verfügbar, einfach zu bedienendes Werkzeug mit einer feinen Spitze, die es angemessen für die Arbeit an kleinen Augen macht, wiein Mäusen. Seine Anwendung verhindert eine unnötige Gefahr für das Auge und es zu unerwünschten Verletzungen führt nicht, wie es oft der Fall bei Modellen chemischen Verletzungen. Wie zu einem stumpfen Schaber gegenüber, entfernt sie das Epithel mit der Basalmembran. In diesem Protokoll wurde die Limbus-Bereich zweimal abgerieben, und dann das Ganze wurde Hornhautepithel von Limbus zu Limbus rasiert. Um Stroma Verletzungen zu vermeiden, wurde darauf geachtet, nicht die Hornhautoberfläche zu bürsten einmal wurde das Epithel bereits entfernt. </p>

<p class="jove_content" fo:keep-together.within-page="1"> Innerhalb eines Monats nach dieser Technik durchgeführt wird , 100% der Cornea entwickelt oberflächlichen Neovaskularisation <strong>(Abbildung 1A.</strong> Fotos mit einer Kamera zu einer Spaltlampe unter einem hellen Bereich und Blaufilter verbunden genommen wurden). In 18/20 (90%) der Augen, beteiligt Neovaskularisierung die ganze Hornhautoberfläche <strong>(1A).</strong> In 2/20 (10%), Neovaskularisation wurde in drei von vier Quadranten kornealen beobachtet, aber es erreicht noch...

Watch this Scientific Journal Video about A Simple Mechanical Procedure to Create Limbal Stem Cell Deficiency in Mouse at JoVE.com

A Simple Mechanical Procedure to Create Limbal Stem Cell Deficiency in Mouse

<p class="jove_content"> Der folgende Artikel stellt eine einfache und reproduzierbare Technik effektiv zu einer nachhaltigen Mausmodell der Limbusstammzellinsuffizienzen (LSCD) erstellen. Dieses Tiermodell ist nützlich bei der Prüfung und die Wirksamkeit von Behandlungen für Limbus-Stammzellen Krankheiten verglichen. </p>

Eine einfache mechanische Verfahren Limbusstammzellinsuffizienzen in der Maus zum Erstellen

Limbal stem cell deficiency (LSCD) is a state of malfunction or loss of limbal epithelial stem cells, after which the corneal epithelium is replaced with ...

a-simple-mechanical-procedure-to-create-limbal-stem-cell-deficiency

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8.3K Aufrufe.  University of Illinois at Chicago.  Der folgende Artikel stellt eine einfache und reproduzierbare Technik effektiv zu einer nachhaltigen Mausmodell der Limbusstammzellinsuffizienzen (LSCD) erstellen. Dieses Tiermodell ist nützlich bei der Prüfung und die Wirksamkeit von Behandlungen für Limbus-Stammzellen Krankheiten verglichen. 

Serie: A Simple Mechanical Procedure to Create Limbal Stem Cell Deficiency in Mouse

Evolutionary Relationships

<p>Humans have been attempting to properly classify living things since Aristotle made the first attempt during the 4<sup>th</sup> century BC. Aristotle&#8217;s system was improved upon during the Renaissance and then, subsequently, by Carolus Linnaeus in the mid 1700&#8217;s. These more formal classification and organization systems grouped species by their physical similarity to one another. For example, all vertebrates have a backbone, but invertebrates do not. Traits like the backbone are called synapomorphies, which are traits that are shared by a group of organisms, presumably because they were derived from a common ancestor. As we will explore, this method has been shown to have limitations and has more recently been amended to include genetic analysis. Still, scientists construct trees called dendrograms to create a visual representation of how species are related to one another and share common ancestors. These dendrograms can aid in our understanding of the evolutionary processes that drive these relationships. Genetic comparisons have added an important tool guiding the analysis of evolutionary relationships.</p>
<h4>Types of Dendrogram</h4>
<p>A type of dendrogram, called a cladogram, depicts the hypothetical genealogical relationships between species with the tips (or leaves) of the tree representing a species and the branches showing how species are related to each other. A slightly more complicated type of tree, called a phylogram, differs from a cladogram in that the branches leading to the species are of different lengths. The length of a branch in this type of tree represents the degree of change between species: the longer the branch, the more time since the species have diverged from a common ancestor. In both types of tree, the common ancestor of a group of species is indicated by a node, which is the point where a series of branches meet. Species that are more closely related to each other (most recently shared a common ancestor) will be located closest to the node. The two species that share a node are called a sister group<sup>1</sup>.</p>
<h4>Understanding Evolutionary Relationships using Genetic Data</h4>
<p>Historically, cladograms were constructed by comparing the morphology (physical structure) of organisms. This method is still practiced but the techniques have been modernized to include comparison of DNA (deoxyribonucleic acid) sequences between species. Using DNA for building trees has several advantages over relying solely on morphology, including being able to calculate an estimate of how long ago different species shared a common ancestor<sup>1</sup>. However, using DNA is not always feasible, especially when trees include extinct organisms. DNA is best found in soft tissues, which are not preserved during the fossilization process, and therefore it is uncommon for a DNA sample of an extinct species to be available.</p>
<p>DNA is passed on from parents to their offspring in hereditary units called genes. The nucleotide (A, G, C, and T) sequence of genes found in different species are frequently quite similar, likely due to their having come from a common ancestor. This fact allows researchers to align sequences from different species with one another to build the trees described above. Species with more similarity between their nucleotide sequences will be placed next to each other in a tree, and species with less sequence similarity will be placed further apart from each other.</p>
<p>Bioinformatics are the tools used by biologists to analyze large datasets using a combination of computer science, mathematical modeling, and statistics. One such tool is called BLAST (Basic Local Alignment Search Tool), which can be used to quickly search the entire genome of any species that is available in the NCBI (National Center for Biotechnology Information) database<sup>2</sup>. The NCBI database combines several different databases that hold different types of DNA sequence information. The process of a BLAST search includes complex computer algorithms, but basically, BLAST aligns sequences of each nucleotide base from a submitted DNA sequence (known as the <em>query</em> sequence) with sequences in the data base that most closely match it. The DNA sequences that are found will be listed in order of similarity to the sequence in question, and will therefore be from species closely related to the species containing the query gene. This comparison may or may not depict the actual evolutionary relationship between species because genes evolve at different rates. Additionally, genomes sometimes contain more than one instance of a similar sequence.</p>
<p>Comparison of DNA sequences of genes is valuable beyond consideration of evolutionary relationships. Frequently, genes are identified in model organisms, such as the fruit fly, <em>Drosophila melanogaster</em>, or the mouse<sup>3</sup>. Integral to studying a gene, the function of its product is commonly identified and analyzed. If a researcher is interested in studying that function in a different organism (humans for example), BLAST or other bioinformatic tools can be used to find candidate genes based on their similarities to the genes of known function from model organisms.</p>
<p>Human genes can also be used as the starting point to find homologs in model organisms. In fact, human disease research depends heavily on this. Once a human gene of interest is identified, mice can be genetically manipulated to have the homologous gene disrupted, or &#8220;knocked out,&#8221; creating a model of the human disease that can be studied in order to understand and treat the disease. There are many of these mouse strains currently available. For example, there is a mouse model for human Cystic Fibrosis (CF) called the <em>Cftr</em> knockout mouse and another modeling atherosclerosis, called the <em>Apoe</em> knockout<sup>3</sup>.<br />
 </p>
<h4>References:</h4>
<ol class="references">
	<li><strong>Annenberg Learner.</strong> Online Textbook: Unit 3 Evolution and Phylogenetics. <em>Rediscovering Biology. </em>[Online] 2017. [Cited: August 23, 2018.] https://www.learner.org/courses/biology/textbook/compev/compev_3.html.</li>
	<li><strong>National Center for Biotechnology Information, U.S. National Library of Medicine.</strong> BLAST: Basic Local Alignment Search Tool. [Online] https://blast.ncbi.nlm.nih.gov/Blast.cgi.</li>
	<li><strong>National Human Genome Research Institute.</strong> Background on Mouse as a Model Organism. <em>National Human Genome Research Institute. </em>[Online] December 2002. [Cited: August 23, 2018.] <a href="https://www.genome.gov/10005834/background-on-mouse-as-a-model-organism/" target="__blank">https://www.genome.gov/10005834/background-on-mouse-as-a-model-organism/</a>.</li>
</ol>

Evolutionary Relationships: Using BLAST to Test Evolutionary Hypotheses - Concept

Evolutionäre Beziehungen

Humans have been attempting to properly classify living things since Aristotle made the first attempt during the 4th century BC. Aristotle&#8217;s system ...

Lehre

JoVE Lab Manual

Biologie

Evolution

Lab Techniques

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse=""><strong>Determining the Density of an Egg</strong><button class="expand">Expand</button>
	<p>Density is a measure of how compact a substance or object is, and it is calculated as mass divided by volume. When a dense object is placed in a liquid with a lower density, the object sinks; when the object is less dense than the liquid, it floats. When the densities are the same, the object will be suspended in the liquid. In this experiment, we&#39;ll determine the density of an egg by creating a solution with the same density. We&#39;ll measure the density of the salt solution using different volume measurement glassware and determine which is the most accurate.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-1">
		<div class="lab-step">To begin, wear the appropriate personal protective equipment, including close-toed shoes, long pants, long-sleeved shirt, lab coat, chemical splash goggles, and gloves.</div>
		</li>
		<li data-sub-note-item="1-2">
		<div class="lab-step">Measure the mass of the egg. Set a weigh boat on the balance and tare it. Carefully set the egg in the weigh boat while you record the mass in your notebook.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Prepare the salt solution that will be used to suspend your egg. Use the 600-mL beaker and fill it 3/4 of the way full with deionized water.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Gently place your egg in the beaker, and then add about one teaspoon of NaCl into the water. Stir the solution gently until the NaCl dissolves. Continue to add NaCl until the egg floats just below the surface.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Use different glassware to measure the volume of the salt solution. Weigh the 50-mL graduated cylinder on the top loading balance and record the mass. Then, measure 20 mL of your salt solution and record the volume in your notebook. <strong>Note: </strong>Place a blank sheet of paper behind the graduated cylinder to read the volume more clearly. Always view the measurement at eye level and measure the volume from the bottom of the meniscus. The lines on the graduated cylinder are 0.2 mL apart, meaning that you can read the volume to the hundredths place.
		<h4><b>Table 1: Measuring Mass</b></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td style="text-align: center;"><strong>Container</strong></td>
					<td style="text-align: center;"><strong>Mass of empty container (g)</strong></td>
					<td style="text-align: center;"><strong>Mass of full containter (g)</strong></td>
					<td style="text-align: center;"><strong>Mass of solution (g)</strong></td>
					<td style="text-align: center;"><strong>Percent error</strong></td>
				</tr>
				<tr>
					<td>50-mL graduated cylinder</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>10-mL volumetric pipette</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>50-mL beaker</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>20-mL volumetric flask</td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/41/Table_1._Measuring_Mass.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Weigh the filled graduated cylinder and record the mass in your notebook. Then, pour the salt solution back into the 600-mL beaker.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Use the volumetric pipette to measure volume. First, weigh the empty 50-mL beaker and record the mass in your notebook. Then, carefully measure 10 mL of the salt solution using the volumetric pipette and dispense the salt solution into the beaker.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Measure another 10 mL and add it to the beaker. Weigh the filled beaker and record the mass in your notebook. Then, empty, rinse, and dry the beaker.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Use the volumetric flask to measure volume. Weigh the empty 20-mL volumetric flask and record the mass. Then, carefully fill the flask with the salt solution to just below the 20-mL fill mark. Do not fill it all the way. Use an eyedropper to finish filling the flask so that the bottom of the meniscus just touches the fill line on the neck of the flask. Then, weigh the full flask and record the weight.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Lastly, use the 50-mL beaker to measure volume. Weigh the empty beaker, then fill the beaker with salt solution to the 20-mL line and weigh the full beaker. Record the masses in your notebook.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Measure the displacement of the egg when it is submerged in the salt solution. First, remove the egg and look at the level of the salt solution in the 600-mL beaker. <strong>Note:</strong> If it is not at a marked line, add deionized water to the solution so that the meniscus is at a readable volume and record the volume.&#160;
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Measurements</strong></td>
					<td><strong>Salt solution using 20-mL volumetric flask&#160;</strong></td>
					<td><strong>Egg</strong></td>
				</tr>
				<tr>
					<td>Mass (g)</td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Displacement of water (cm)</td>
					<td style="text-align: center;">-</td>
					<td></td>
				</tr>
				<tr>
					<td>Inner diameter of 600-mL beaker (cm)</td>
					<td style="text-align: center;">-</td>
					<td></td>
				</tr>
				<tr>
					<td>Volume (cm&#179;)</td>
					<td style="text-align: center;">-</td>
					<td></td>
				</tr>
				<tr>
					<td>Volume (mL)</td>
					<td style="text-align: center;">20</td>
					<td></td>
				</tr>
				<tr>
					<td>Density (g/mL)</td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<strong><a href="https://www.jove.com/CDNSource/lm/labs/41/Table_2._Measuring_Density.xlsx" target="_blank">Click Here to download Table 2</a> </strong></div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Gently place the egg in the beaker.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Use a ruler to measure the new height of the solution level and record the height. Then, place the ruler across the top of the beaker to measure the inner diameter.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Calculate the new volume from these measurements. Subtract the initial volume to obtain the displacement of the egg (volume).</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">To clean up from the experiment, return the egg to your instructor and pour the salt solution down the sink. Rinse all used glassware with tap water and set them out to dry. Finally, return the sodium chloride to your instructor.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse=""><strong>Results</strong><button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">Calculate the mass of the solution in each of the different volumetric glassware by subtracting the empty glassware mass from the full glassware mass.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Keep track of uncertainty in your measurement by using significant figures. For example, when we look at the graduated cylinder measurement, the weight of the empty container is 90.92, and the weight of the full container is 111.59. The weight measurements have significant figures to the hundredths place, so it is important that significant figures are maintained throughout our calculations. Thus, the mass of the 20-mL salt solution is 20.67 g.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">The 50-mL beaker weighed 28.65 g when it was empty and 47.96 g when it contained 20 mL of salt solution. Therefore, the mass of 20 mL of the salt solution is 19.31 g.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Repeat the calculation to obtain the mass of 20 mL of salt solution that was measured using the 10-mL pipette and the 200-mL volumetric flask.<b> Note:</b> Generally speaking, volumetric measurements are more accurate when using a volumetric flask.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Look at the accuracy of the other methods compared to the volumetric flask in terms of percent error. Percent error is calculated by subtracting the theoretical value from the experimental value, then dividing by the theoretical value times 100.
		<ul>
			<li><img src="https://www.jove.com/CDNSource/lm/labs/41/41_Procedure_1b.jpg" /></li>
		</ul>
		</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Use the volumetric flask measurement as the theoretical value to determine the percent error for the other volume measurement methods. As expected, the volume measurement that uses the markings on the beaker is the least accurate.<strong> Note: </strong>We also know this because the known density of pure water is 1 g/mL. Thus, 20 mL of pure water weighs 20 g. The density of the salt solution must be higher than 20 g since salt was added to the water.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Calculate the density of the salt solution using the volumetric flask measurement. Divide the mass of the solution by the volume of the solution. Thus, the density of the salt solution is 1.053 g/mL.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Compare the calculated density of the salt solution to the density of the egg. The volume calculated using the displacement of water in a beaker was found to be 61.14 cm<sup>3</sup> or 61.14 mL. The weight of the egg was measured to be 60.15 g, so its density is 0.9838 g/mL. The disparity between the density of the egg and the density of the salt solution arises from error introduced in both calculations, primarily due to volume measurement readings.</div>
		</li>
	</ul>
	</li>
</ol>

Accuracy, Precision, Uncertainty, and Significant Figures - Procedure

Labortechniken

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Determining the Density of an EggExpand
	Density is a measure of how compact a substance or ...

Chemie

Lab Manual Sub Articles

Bacterial Transformation

<ol class="note-items"><li data-note-item="1" data-parent-collapse=""><strong>Bacterial Transformation</strong>
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">IMPORTANT: In addition to wearing the appropriate personal protective equipment, be sure to take care to keep your face away from suspension cultures, and to avoid inhaling reagents. Do not touch your face while performing the experiment. Always wash your hands before and after every experiment.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">When you are ready to safely begin, check to make sure you have a tube or tubes of competent <em>E. coli</em> cells in your ice bucket.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, transfer 50 &#181;L from one of these tubes to each of two new micro-centrifuge tubes, one labeled '&#8211;', and one labeled '+'.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Next, pipet 2 &#181;L of p-GREEN plasmid into the plus tube and flick the tube gently to incorporate the plasmid throughout the bacterial solution. HYPOTHESES: The experimental hypothesis is that on plates containing no antibiotic, bacteria with or without the plasmid can survive, and so both will grow lawns of bacteria. Conversely, on the plates containing the ampicillin antibiotic, only the bacteria successfully transformed with the resistance plasmid will grow, whereas the minus plasmid plates will contain no bacteria. The null hypothesis of this experiment is that there will be no difference in bacterial growth between the plates.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Incubate both tubes on ice.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">After 30 minutes submerge both tubes 3/4 of the way into the water of a 42 &#176;C water bath for 30 seconds.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">At the end of the water bath incubation, place the tubes back on ice for 5minutes, then add 950 &#956;L of room temperature SOC media to each tube.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">Incubate the tubes in a shaker at 37 &#176;C for 60 minutes at 250 rpm.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">While the tubes are incubating, label the bottoms of one LB and one LB/ampicillin, or AMP plate, &#8220;+ plasmid&#8221;, and the bottoms of one LB plate and one LB/AMP plate &#8220;- plasmid&#8221;.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">At the end of the incubation, pipet 50 &#956;L from the &#8220;+ plasmid&#8221; cell tube onto both the LB/AMP plus plate and the LB plus plate.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Then, with a fresh tip, add 50 &#956;L of the bacteria that were not exposed to the plasmid to each of the minus plates.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Then, spread each plate using a fresh pipette tip.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Cover the plates with their lids, and then seal them with laboratory film.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Then store the plates upside down in a 37 &#176;C incubator for 24 hours.
</div></li></ul></li><li data-note-item="2" data-parent-collapse=""><strong>Results</strong>
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">The day after the transformation, observe which plates have bacteria, and how the bacteria are distributed over each plate.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Record the number of colonies and the color of the colonies for different conditions. <a href="https://www.jove.com/CDNSource/lm/labs/11/Table_1_Bacterial_Transformation.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="2-3"><div class="lab-step">To determine the initial mass, IM, of the plasmid, first multiply the plasmid concentration from the stock tube of p-GREEN by the volume transferred into the experimental tube.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">To calculate how much DNA is spread onto each plate, divide the volume of bacterial suspension spread onto each plate by the volume of the suspension in the tube, and multiply this fraction by the initial mass of plasmid used.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">To determine the transformation efficiency, count all of the visibly distinct colonies on the plus plasmid LB/AMP plate, and divide this number by the mass of plasmid spread. NOTE: The unit for transformation efficiencies is cfu/&#956;g of plasmid DNA.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Record all of the results for each plate in the table and analyze them.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Observe any differences between the colonies and make hypotheses to explain this observation. Consider the factors that may affect the transformation efficiency of competent bacteria.
</div></li><li data-sub-note-item="2-8"><div class="lab-step">NOTE: You will have also noticed that each plate had a different outcome. The minus plasmid and plus plasmid LB plates should have grown a lot of bacteria across their plates. The minus plasmid LB/AMP plate should have no bacterial growth. And the plus plasmid LB/AMP plate should have grown bacterial colonies that fluoresced green.
</div></li></ul></li></ol>

Bacterial Transformation using Plasmids - Procedure

Bakterielle Transformation

Bacterial Transformation
ExpandIMPORTANT: In addition to wearing the appropriate personal protective equipment, be sure to take care to keep your face ...

Genetik

Genetics of Organisms

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">REF and WEF Fly Genetics
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">NOTE: At your station, you should have four vials of flies. They will be labeled as male or female. They will also be labeled with the notation REF for red-eyed flies or WEF for white-eyed flies. The female vial should also be labeled virgin as these flies should be unmated for the purpose of this experiment.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Make sure you have around five flies in each vial. NOTE: You will perform crosses using these flies to determine if red or white eyes is dominant and if the trait is sex-linked. You should also have two fly anesthesia wands, a paint brush, magnifying glass, fly anesthetic, some empty fly vials, and a sheet of white paper.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Draw a line in the middle of the paper to make a male side and a female side.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Dip the fly anesthesia wand into the solution and insert it into the red-eyed female vial until the flies stop moving.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Then, dip the same wand into the white-eyed male vial until these flies are also anesthetized.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Tap the flies from the two vials onto the sheet - Females on one side and males on the other.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Check to make sure that all the flies from the female vial are female and likewise, confirm that the male flies are male.  NOTE: Males are slightly smaller and have a darker solid pigment on the end of their abdomen. Females are larger and have stripes rather than a solid spot.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">If there are any male flies in the female vial, obtain a new vial as these females likely have sperm from males from their own strain and are unusable.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Now, move the five red-eyed females and five white-eyed males into a new vial using the paintbrush.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Label this vial to indicate that this is a cross between red-eyed females and white-eyed males. HYPOTHESES: Use Punnett squares to formulate hypotheses for this experiment. Consider what you will see in a few days if the white allele is dominant and there is no effect of parental sex. What if red is dominant? Under the potential offspring genotype in each box, write the expected phenotype.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">To set up the reverse cross, again dip the fly anesthesia wand into the solution and insert it this time into the white-eyed female vial and then the red-eyed male vial until all the flies have stopped moving.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Tap the flies onto a sheet of white paper and check to make sure that all the flies from the female vial are female and likewise with the male flies.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Now, move the five white-eyed females and five red-eyed males into a new vial using the paintbrush.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Label this vial to indicate that this is a cross between white-eyed females and red-eyed males.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Finally, place the two tubes containing the new crosses into a rack for incubation at room temperature. NOTE: After about three days, larvae should be moving around in the vial.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Remove the 10 adult flies and dispose of them into the morgue tube containing 70% ethanol.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Now, put the tubes back in the rack and let the larvae mature until they reach the adult stage in up to two weeks.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Once all of the larvae from these crosses have matured to adulthood, anesthetize the flies in one of the tubes using the wand.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">Then, on a piece of white paper, sort the flies by sex and phenotype and then record these data.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Now, repeat this process and tally the sexes and phenotypes for the second cross (steps 1 &#8211; 18).
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Finally, once you have counted all of your flies, dispose of them in the morgue vial.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">To begin investigating your results, first compare the data you collected with the hypothesis you made using the Punnett squares.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Did your data match the simple Punnett square hypothesis where red or white is dominant and there is no effect of sex? Compare your data with other lab groups.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">If your data does not match what your Punnett squares predicted, does this indicate that the gene may be sex-linked?
</div></li><li data-sub-note-item="2-4"><div class="lab-step">If the red gene were dominant and sex-linked, when we cross red-eyed females with white-eyed males, all of the offspring would have red eyes. Assuming all of the females were homozygous for the color allele, does this match your data for the first cross?
</div></li><li data-sub-note-item="2-5"><div class="lab-step">If white were dominant and the gene were sex-linked, we would see the exact opposite. So all of the flies would have white eyes. From your data, can you conclude from your first cross whether red or white is dominant?
</div></li><li data-sub-note-item="2-6"><div class="lab-step">When the reciprocal cross of white-eyed females and red-eyed males is performed, if the red phenotype is dominant, all of the females would be red and all of the males would be white. This would also confirm that the gene is specifically x-linked because white-eyed females could then only be produced in crosses with white-eyed males. Did your second cross produce any white-eyed females?
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Finally, if the gene were x-linked and white was dominant, crossing white-eyed females with red-eyed males would result in all of the offspring having white eyes. Does this hypothesis fit with your second cross?
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Look over your data and conclude which of the hypotheses best fits the patterns you found in your crosses. If your data does not fit with any of these, hypothesize why this might be the case.
</div></li></ul></li></ol>

Genetics of Organisms: REF and WEF Fly Genetics - Procedure

Genetik der Organismen

REF and WEF Fly Genetics
ExpandNOTE: At your station, you should have four vials of flies. They will be labeled as male or female. They will also be ...

Cell Division

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Observing the Cell Cycle in a Root Tip
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">Hypotheses: The experimental hypothesis is that in root tips slices that have been treated with nocodazole, a chemical that interferes with microtubular polymerization, all of the cells will be arrested at the same stage of the cell cycle and that in untreated onion tip slices all of the different stages of the cell cycle will be visualized. The null hypothesis is that there will be no differences in mitosis between the two groups and that different stages of the cell cycle will be visualized. 
</div></li><li data-sub-note-item="1-2"><div class="lab-step">To prepare for this experiment you will use an onion that has been placed in water for several days until new white root tips have begun to sprout. Use a razor blade to cut a 1 cm piece from the end of one of the root tips. 
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Place the slice of onion into a microcentrifuge tube labeled &#8220;N&#8221; for the nocodazole condition. 
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Then, cut a second 1 cm piece of onion root tip and place in a microcentrifuge tube labeled &#8220;C&#8221; for the control condition.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Add 2 &#181;L of the 5 mg/mL nocodazole to 1 mL of water in the microcentrifuge tube labeled N and 1 mL of water only to the tube labeled C. 
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Leave the tubes containing the root tips to incubate for 12 hours and wipe down the workspace with 70% ethanol.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">When incubation is complete, set a heat block to 60 &#186;C.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">Wash the nocodazole treated tips with water and then aspirate the liquid.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Repeat this wash two more times, for a total of three washes. 
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Fill both tubes with 1 mL of one normal hydrochloric acid. Incubate the tubes in a 60 &#186;C heat block for 12 - 15 min, then discard the acid into a waste flask.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Now, add 1 mL of distilled water drop wise to the tubes at least three times to rinse the samples.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Now add one microliter of DAPI stain to 10 mL of phosphate buffered saline (PBS).
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Then place 50 &#181;L of this dilute DAPI stain into each tube, and leave them at room temperature to incubate for 12 min. 
</div></li><li data-sub-note-item="1-14"><div class="lab-step">After this, preform three distilled water washes as in step 10. 
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Label one microscope slide as 'Control' and another as 'Nocodazole'. 
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Transfer the stained roots onto their respective microscope slides and add a drop of water to the control slide and a drop of nocodazole to the nocodazole slide.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Use the razor blade to remove the unstained portions of each root tip and place a glass cover slip over each sample.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Carefully press down on each cover slip with a gloved fingertip, and then let the slides sit for 10 min. 
</div></li><li data-sub-note-item="1-19"><div class="lab-step">Finally, view the slides under the 40X objective of a fluorescence microscope and capture images of your root tip cell preparations.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Understanding the Loss of Cell Cycle Control
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">NOTE: Before cells can pass through all of the stages of the cell cycle there are several checkpoints they must go through. These checkpoints are regulated by cyclin and cyclin-dependent kinase proteins, or CDKs. If the cyclins and CDKs determine that previous cellular events have not been adequately completed they will arrest the cells at this step and prevent them from proliferating. In cancer cells one or several of these molecular restraints for regulating cell division are lost and this allows the damaged cells to escape from cell proliferation control. These abnormal cells develop into tumors which are masses of uncontrolled proliferating cells that interfere with the normal functions of the body. Notice how before it divides this cancer cell rounds up and refracts light very strongly under the light microscope. This is because not all cancer cells successfully divide into daughter cells after each round of mitosis. This will mean that they often contain an excess of organelles and DNA and this increase in cellular content means they will refract light more intensely than normal cells do. 
</div></li></ul></li><li data-note-item="3" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="3-1"><div class="lab-step">Examine your collected images and record in Table 1 the different cell structures and stages that could be identified in the onion tip slice that was treated with nocodazole. <a href="https://www.jove.com/CDNSource/lm/labs/10/Table_1_Cell_division.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="3-2"><div class="lab-step">If there are any cells undergoing mitosis, note what stages of cell division you see.
</div></li><li data-sub-note-item="3-3"><div class="lab-step">Record the percentage of cells in each stage of mitosis in Table 1. 
</div></li><li data-sub-note-item="3-4"><div class="lab-step">Next, examine the images of the untreated onion tip slice, and record what cell structures can you identify. 
</div></li><li data-sub-note-item="3-5"><div class="lab-step">If there are any cells undergoing mitosis, consider what stages of cell division you see, and record the percentages of cells in each stage of mitosis in the Table 1. 
</div></li></ul></li></ol>

Cell Division: Observing Cell Cycle in a Root Tip - Procedure

Zellteilung

Observing the Cell Cycle in a Root Tip
ExpandHypotheses: The experimental hypothesis is that in root tips slices that have been treated with nocodazole, a ...

Zellprozesse

Cell Structure

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Visualizing Onion and Human Cells
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">In this experiment you will prepare different types of cells from a plant and animal, onion and human respectively, and then visualize them under a microscope. HYPOTHESES: The experimental hypothesis is that the cells will appear different in overall shape and membrane structure, but there will be some shared similar structures, like nuclei, in both cells. The null hypothesis of the experiment is that there will be no difference in structure between the two cell types.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">First, to prepare an animal cell slide, start by pouring 30 mL of distilled water into a beaker.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, use a glass dropper to place 2 - 3 drops of the water onto the center of a clean microscope slide.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Next, take a clean toothpick and scrape the inside of your cheek to gather cells.  CAUTION: Do not scrape your cheeks too aggressively. The scraping should not cause discomfort or bleeding. 
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Put the end of the toothpick with the cheek cells onto the wetted area of the slide and mix the water and cheek cells together.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Next, add two drops of methylene blue staining solution to the wetted area of the slide and mix it in with a clean toothpick.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Let the mixture sit at room temperature for 3 minutes.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">After 3 minutes have passed, use a glass dropper to add a drop of glycerol to the mixture.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Carefully, place a cover slip over the mix on the slide by first standing one end of the cover slip vertically and aligning it along to one side of the mixture. Then, carefully lower the other end of the cover slip down until the mixture is completely covered.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Finally, remove any excess liquid with blotting paper.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Next, prepare a slide of plant cells by placing five drops of distilled water into a clean watch glass.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Then, with forceps, take a thin strip of onion and place it into the water.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Apply 5 drops of safranin solution to another watch glass.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Now using a pair of forceps transfer the piece of onion from the distilled water into the safranin.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Allow the onion to soak for 30 seconds.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Then, again with forceps, move the onion back into the distilled water.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Now, place 3 drops of glycerol onto the center of a glass microscope slide.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Using the forceps again, transfer the onion into the glycerol on the slide.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">Gently place a cover slip over the onion on the slide and blot away any excess liquid with a piece of blotting paper.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Next, you will visualize the slides you have prepared using a compound microscope. First, turn on the scope and set the objective lens to the lowest level of magnification.  NOTE: A compound microscope typically has two levels of magnification.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Place the cheek tissue slide onto the stage of the microscope and bring the cells into focus by adjusting the stage and using the coarse adjustment knob.
</div></li><li data-sub-note-item="1-22"><div class="lab-step">When the cells are in focus, observe the individual cells and draw what you see. Repeat these observations at medium and high magnifications adjusting the focus with the fine adjustment knob. IMPORTANT: Do NOT use the coarse adjustment knob at high magnifications. 
</div></li><li data-sub-note-item="1-23"><div class="lab-step">Next, rotate the nose piece so that the oil lens is almost in place.
</div></li><li data-sub-note-item="1-24"><div class="lab-step">Place a drop of immersion oil on top of the cover slip of the cheek cell slide.
</div></li><li data-sub-note-item="1-25"><div class="lab-step">Use the oil lens to view the cheek cells and record your observations.
</div></li><li data-sub-note-item="1-26"><div class="lab-step">Repeat these steps to view the onion plant cell, moving again from low to medium, high, and oil lenses (steps 20 &#8211; 24).
</div></li><li data-sub-note-item="1-27"><div class="lab-step">Record all of your observations and note the differences you see between animal and plant cells.
</div></li><li data-sub-note-item="1-28"><div class="lab-step">When you are finished, place the cheek cell slide and toothpicks into a diluted bleach solution. Dispose of the cover slips into a glass waste container.
</div></li><li data-sub-note-item="1-29"><div class="lab-step">Finally, turn off the microscope and clean the lenses with lens cleaning paper.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">Calculate the total magnification for each of the viewing levels. Remember to account for both the eyepiece magnification and the objective lens magnification. NOTE: Eye piece: 10X magnification, Objective lens: 4X, 10X, and 40X magnification
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, identify the structural differences between plant and animal cells using the observations made under the microscope.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Label the nuclei in both cell types and then highlight or note any differences that you see between them.
</div></li></ul></li></ol>

Cell Structure: Visualizing Onion and Human Cells - Procedure

Zellstruktur

Visualizing Onion and Human Cells
ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human ...

GRUNDLAGEN

Extinction

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Diversity and Extinction during the Paleogene Epoch
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">Begin this procedure by reading the extinction reading supplement that has been printed out for you. <br /><strong>NOTE:</strong> Alternatively, you may download the reading supplement at the link below.&nbsp; <a href="https://www.jove.com/CDNSource/lm/labs/24/Lab_20_Reading Supplement.docx" style="display:block;margin:20px;" target="_blank">Click here to download the extinction reading supplement</a>
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Using the information contained in the extinction reading supplements pertaining to the taxa of interest and the Chicxulub impact event, make predictions for each taxon listed in Table 1. Consider whether diversity in each taxon increased, decreased, or stayed the same immediately following the Cretaceous-Paleogene boundary and later on in the Paleogene epoch. <a href="https://www.jove.com/CDNSource/lm/labs/24/Table_1_Extinction.xlsx" style="display:block;margin:20px;" target="_blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, fill out the reasons for each of your predictions in the Contributing Factors column. HYPOTHESES: The experimental hypothesis is that many of the different taxa will show changes in diversity after the Cretaceous-Paleogene event, and again at the end of the Paleogene, with some increasing in diversity, while others decrease. The null hypothesis is that there will be no changes in diversity between taxa following the Cretaceous-Paleogene event, or at the end of the Paleogene.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Gather diversity data by going to the Paleobiology Database: <a href="http://www.paleobiodb.org" target="_blank">www.paleobiodb.org</a>.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">In the center of the screen, click the yellow box labeled Download Data. Under the italicized heading, &#8220;What do you want to download?&#8221;, select Diversity over time on the left side and Comma-separated values on the right side.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Scroll down to the heading &#8220;Select by taxonomy&#8221;.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">In the first box labeled 'Taxon or taxa to include', type in the name of the taxon that data is being gathered on.  NOTE: Ensure the spelling is correct.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">Now, go to the dropdown menu right below that box labeled &#8220;Taxonomic resolution&#8221;, and select genera.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Under the next heading, Select by time, type Maastrichtian into the first box and Chattian in the box directly below. Make sure the dropdown menu labeled Time rule is set to major and the Temporal resolution is set to stage.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Select &#8220;Assume extant taxa range through to present&#8221;. Scroll back up to the middle of the page and click download. A save window will open.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Save the .csv file to a safe and accessible place and rename it to make it easy to identify.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Open the file and scroll down to the main dataset under Records.  NOTE: The data are arranged in reverse time order by geological stage. The second column, interval_name, gives the accepted name of the stage in question. The next two columns give the appropriate dates of the stage in millions of years before the present. The final column, number of occurrences, gives a total count of the genera extant during that geological stage as determined from occurrence of fossils.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">To more easily work with this data, copy and paste each column into a new sheet. Be sure to label this sheet with the taxon in question, the data and time the data were obtained, and the data source.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Repeat this process for each of the taxa in Table 1 (steps 4 &#8211; 12). NOTE: Data from multiple taxa can be kept on the same sheet, so long as they are kept distinct and labeled appropriately.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">To create line plots for each of the taxa showing the change in diversity over time, select the max_ma column and the number of occurrences column simultaneously.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">In Excel, select Insert from the top toolbar and find the section labeled Charts. Select the bottom center icon, Insert Scatter Chart.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Then, select the Scatter with Straight Lines and Markers and a graph should appear. NOTE: Since the axis of this graph is in units of millions of years ago, the axis is in the reverse direction of time when put in numerical order.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">To fix this, click on the green plus sign in the top-right corner of the graph and hover over Axes. This should reveal a small black arrow. Click the arrow to open up a small menu and select More Options.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">This will open the Axis Options menu. Under Axis Options, click the box next to Values in reverse order. NOTE: It is also possible to change the axis scales from this menu, which can be used to eliminate the excess time that is not being analyzed in this lab. Keep any changes consistent between different graphs.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Double-click on the title at the top of the graph and change it to the taxon being represented.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Make a separate graph for each of the taxa in Table 1. Keep them organized and in one location. A separate sheet for graphs is recommended.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">For each graph, identify the location of the Cretaceous-Paleogene boundary and draw a vertical line through the graph at this point.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Using the information from the graphs, fill out Table 2. In some cases, it may be helpful to go back to the original dataset and compare actual values, particularly when they are small. <a href="https://www.jove.com/CDNSource/lm/labs/24/Table_2_Extinction.xlsx" style="display:block;margin:20px;" target="_blank">Click Here to download Table 2</a>
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Compare these values to the predictions made in Table 1 and discuss if the original contributing factors are still likely candidates.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Using the dataset, calculate the percentage of total taxa that went extinct over the Cretaceous-Paleogene boundary using this equation.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">There is an event in the middle of the Paleogene known as the Paleocene-Eocene Thermal Maximum about 55.5 million years ago. This represents a high point in temperature during the Paleogene epoch at approximately 8 &#176;C higher than today&#39;s average temperature. Does this point seem to have an effect on diversity for any of the taxa? If yes, then which ones?
</div></li></ul></li></ol>

Extinction: Diversity and Extinction during the Paleogene Epoch - Procedure

Aussterben

Diversity and Extinction during the Paleogene Epoch
ExpandBegin this procedure by reading the extinction reading supplement that has been printed out for ...

Ökologie

Transpiration

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Comparing Transpiration Rates of Leaves
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">To begin the experiment to measure the transpiration rates of leaves from different plant species, you will first create a tool called a potometer, using a piece of plastic tubing and 5 mL calibrated pipette.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">To assemble the device, simply attach the rubber tubing to the tip of the pipette.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, submerge the device into a bucket of water and move the pipette around under the water to fully fill the tube, taking care not to create bubbles.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Next, cap the open end of the tube with a pipette bulb to keep the water in.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Now, taking care not to spill water from the potometer, use a clamp and stand to hold the capped end of the pipette around 1 - 3 inches below the pipette bulb.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Then, use a second clamp attached lower on the same stand to secure the open end of the rubber tubing.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Next, use a transfer pipette or dropper to remove water from the open end of the tubing until the water level in the pipette portion of the potometer rests at the zero line. HYPOTHESES: In this experiment, the experimental hypothesis might be that leaves from plant species more adapted to hotter or arid environments will have lower transpiration rates than those from humid or wet regions. The null hypothesis would be that leaves of the different plant species will not differ in their transpiration rates.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">To begin the experiment, carefully use scissors to cut the end of the petiole, or stalk, of the first leaf and then insert the leaf into the tubing.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Then, place a layer of lubricant around the area where the plant stem and rubber tubing meet to make a watertight seal.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Next, remove the pipette bulb and taking care not to disturb the setup, let the experiment run for the appropriate experimental period, typically 30 - 60 minutes.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">At the end of the allocated time, record the level of the water in the pipette, noting how much the level dropped in milliliters.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Then, refill and reset the potometer water level to zero, and then repeat the procedure for each of the remaining test leaves until the transpiration rates of all four leaves have been measured.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Next, to determine the surface area of the leaf samples, lay each leaf on a blank piece of paper and carefully trace the outlines.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Then, cut the outlines out and record the mass of each tracing.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Finally, cut out and weigh one four by four centimeter square of the same type of paper used to make the leaf tracings. This will act as a reference with known area and weight.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Next, you will need to quantify the number of stomata per unit area on each leaf. To do this, first prepare a slide mount by painting at least one square centimeter of the underside of each leaf with clear nail polish. IMPORTANT: Ensure you paint the bottom of the leaf, since the majority of the stomata are located there. 
</div></li><li data-sub-note-item="1-17"><div class="lab-step">When the nail polish is completely dry, carefully press a small piece of cellophane tape directly onto each patch and then gently peel off the tape to remove the painted on polish. NOTE: Use a piece of tape that is smaller than the microscope slide. 
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Then, place each impression and tape onto a separate, clean microscope slide. HYPOTHESES: In this exercise, the alternative hypothesis could be that the leaves of the plants adapted to drier environments will have fewer stomata per unit area than the leaves of plants adapted to wetter environments. The null hypothesis might be that all plants species will have an equal number of stomata per unit area.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">To observe each impression under the microscope, first use a low magnification to find areas of the leaf impression that contain stomata. These will appear as darker dots or impressions.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Then, switch to a higher magnification, keeping the sample viewing window centered on the stomata-containing area.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Draw and label your observations, making sure to label each sketch with the plant species.
</div></li><li data-sub-note-item="1-22"><div class="lab-step">Then, count and record the number of stomata in the field of view. You should perform this count a total of four times in four different areas of the leaf impression, and then determine the average number of stomata per counted area on the leaf.
</div></li><li data-sub-note-item="1-23"><div class="lab-step">To calculate the number of stomata per mm<sup>2</sup>, place a transparent plastic ruler on the microscope stage under the objective and measure the diameter of the field of view.
</div></li><li data-sub-note-item="1-24"><div class="lab-step">You can then use this number, the diameter or D, to calculate the area of the field of view in mm<sup>2</sup>.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">First, calculate the surface area of the 4x4 cm paper square to obtain the number of square centimeters.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, divide the weight of the paper square by the number of centimeters squared it covers to obtain the weight of 1 cm<sup>2</sup> of paper.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Finally, to calculate the surface area of each leaf, divide the weight of the leaf tracing by the weight of 1 cm<sup>2</sup> of paper. This will give you leaf area in centimeters squared.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">You should now convert this number to meters squared, the standard unit used for calculating transpiration rate.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">To calculate the transpiration rate for each leaf, divide the total water loss you measured in the potometer in mL by the time the experiment was run for in minutes.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then, divide this by the surface area of the leaf in m<sup>2</sup>.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Make a bar graph with the four different leaf species on the X axis, and their corresponding transpiration rates on the Y axis. Do these rates appear different?
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Next, add a second Y axis to your chart and plot the average number of stomata per millimeter squared for each leaf that was observed under the microscope. Do you see a correlation between transpiration rate and number of stomata? If so, does this seem to have any relationship to the native environment the tree would typically inhabit?
</div></li></ul></li></ol>

Assessing Transpiration Rates using Potometer - Procedure

Comparing Transpiration Rates of Leaves
ExpandTo begin the experiment to measure the transpiration rates of leaves from different plant species, you will ...

Artificial Selection

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Observing Artificial Selection in Plants 
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">To begin the experiment, collect five two-week old grown plants from the generation one population that appear healthy. Note: Plants should appear green, not wilted, and not have damaged leaves. Experimental Hypothesis: The experimental hypothesis for this lab might be that the number of lead trichomes varies naturally, but the average number will increase over generations if only plants with the highest number of trichomes are interbred or decrease if those with the least are interbred. Null Hypothesis: The null hypothesis might be that the average number of trichomes will not change over subsequent generations after artificial selection.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Label each plant with a letter from A to E and with both partners&#8217; names.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Record any natural differences you see between your plant samples. Note: All of the plants are the same age, so any observed variation is due to expressed phenotype, not development.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Use a hand lens to count the number of trichomes found on the petiole of the lowest leaf, not including the round, first-grown cotyledons for each plant. Note: It can be helpful to shine a light onto the plant and to hold it against a dark background, such as a lab bench, during the trichome analysis. 
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Both partners will conduct counts on each plant independently and compare answers. If the counts are different, enlist a third counter or take the average of the two results.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">After this, determine the median number of trichomes for the entire class.  <a target="__blank" style="display:block;padding:20px;" href="https://www.jove.com/CDNSource/lm/labs/2/Lab_2_Table_A.xlsx">Click Here to download Table A</a>
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Determine the top and bottom 10% of the plants from the class trichome count. These groups will make up the two artificially selected lines: high hairiness and low hairiness, respectively.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">If more than 10% of the plants have no trichomes, select 10% of those plants randomly for the low hairiness plant line.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Separate the two groups of selected plants and label them clearly.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Move the plants to a well-lit area and keep them well watered until they develop flowers. Note: Flowers typically develop around 14 days.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">When the flowers are fully developed, use a pollination wand or paintbrush to rub the stigma and anther of one plant&#8217;s flowers for a few seconds.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Using the same wand or brush, rub the inside of each flower of every other plant in the same selection line.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Using a different wand or brush, repeat steps 11 through 12 on the other line. Note: Take care not to cross the lines. Spread the pollen only among the appropriately selected plants.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Return the generation one plants to the growing areas. When the plants reach approximately 1 month old, they should produce mature seed pods.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Allow the plants to dry out once the seed pods turn yellow.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Break the seed pods open and collect the seeds.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Obtain new pots for the generation two seeds.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Fill the pots with moist potting soil about halfway and add a fertilizer pellet to each pot.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">Fill the pots with more soil to fill just below the lip.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Make a shallow depression in the soil of each pot with a probe.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Touch a clean toothpick to a gluestick and use the toothpick to transplant the seeds into the soil one by one.
</div></li><li data-sub-note-item="1-22"><div class="lab-step">Cover the seeds with a thin layer of soil.
</div></li><li data-sub-note-item="1-23"><div class="lab-step">Label the pots with their hairiness line and place them in the designated growing area.
</div></li><li data-sub-note-item="1-24"><div class="lab-step">Use a plastic dropper to water the plants as needed to ensure they do not dry out.
</div></li><li data-sub-note-item="1-25"><div class="lab-step">When the plants are two weeks old, collect five plants from each line and label them A to E.
</div></li><li data-sub-note-item="1-26"><div class="lab-step">Then, count the trichomes on these plants as previously described (steps 4- 5).
<a target="__blank" style="display:block;padding:20px;" href="https://www.jove.com/CDNSource/lm/labs/2/Lab_2_Table_B.xlsx">Click Here to download Table B</a>
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Data Analysis
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">Create a frequency graph based on the generation one class data with the trichome count on the x axis and the number of plants on the y axis. Label the mean. 
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, create frequency graphs for both of the selected hairiness lines.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Compare the frequency graphs for generation one and both hairiness lines.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Take note of phenotypic shifts observed in the selected hairiness lines.
</div></li></ul></li></ol>

Artificial Selection: Visualization in Plants and Data Analysis - Procedure

Künstliche Selektion

Observing Artificial Selection in Plants 
ExpandTo begin the experiment, collect five two-week old grown plants from the generation one population that ...

Physiology of the Circulatory System

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Measuring Circulatory System Function in Humans
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">Before starting the experiment go to the front of the room and collect an alcohol swab, a sphygmomanometer, and a stethoscope.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Clean the earpieces with the alcohol swab and then insert them into your ears.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">To check if the stethoscope is in the on position, gently tap the flat metal disc called the diaphragm.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">If you hear a sound it&#39;s on. If not, turn the metal disc and tap again and keep turning and tapping the disc until you hear a sound. NOTE: For this experiment you will work in pairs. One person will measure their partner&#39;s blood pressure, while the person being measured will count their heartbeats over the course of one minute.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Fill out table one with the name of the person being monitored. HYPOTHESES: The experimental hypothesis is that systolic blood pressure will be higher when the person is sitting when compared to lying down because more pressure is required for blood to be moved around the body. The null hypothesis is that there will be no difference in systolic blood pressure whether a person is sitting or lying down.<a href="https://www.jove.com/CDNSource/lm/labs/9/Table_1_Physiology_of_Circulatory_System.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="1-6"><div class="lab-step">The person being monitored should begin by lying down. Next, they will need to locate their pulse by placing two fingers next to their windpipe. If a throbbing sensation is felt, this is the pulse.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Now, ready a time keeping device to count out 1 minute as the person taking their pulse will be having their blood pressure taken at the same time.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">At this point, the person measuring blood pressure should place the cuff of the sphygmomanometer around the other arm of the subject and the stethoscope earpieces into their own ears.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Start the timer.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">The person being monitored should begin counting the number of heartbeats felt over one full minute. While the subject is taking their pulse, the person taking blood pressure should place the diaphragm of the stethoscope under the cuff on the inside of their partner&#39;s elbow.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Then, pump the cuff to 200 mm of mercury.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Gently and slowly twist the metal knob on the sphygmomanometer to release air from the cuff.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">As pressure is released the first Korotkoff sound should be heard. The corresponding value on the sphygmomanometer is the systolic blood pressure. Consistent sounds should be heard until they die out with the last sound signifying the diastolic blood pressure.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Record the systolic pressure, the diastolic pressure, and the heart rate in Table 1.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Now, repeat the blood pressure and pulse measurements with each partner keeping the same role but this time the subject should be sitting upright.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Record these data in the appropriate places in Table 1.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Finally, the partners should switch spots. So now, the person measuring blood pressure should be taking their pulse and acting as the subject.  NOTE: Be sure to wipe the earpieces of the stethoscope between users and don&#39;t forget to record your measurements in Table 1.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">After finishing the experiment, discard all alcohol swabs into the trash. Then, bring the sphygmomanometer and stethoscope back to the front of the room.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Measuring Respiratory Rate in Fish
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">To prepare for this second experiment, collect two clear containers.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Begin by filling half of one container with aquarium water.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Then, use a fish net to gently catch a goldfish and place it into the cup. Pinch the net around the fish or else it may jump out of the net.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Familiarize yourself with the operculum of the fish. The operculum covers the gills and it is located behind and below the eye. When the fish respires the operculum moves in and out and this is one gill beat. HYPOTHESES: In this experiment you will measure the gill beats of the fish in different water temperatures. The hypothesis is that there will be a significant correlation between the temperature and respiration rate in goldfish. The null hypothesis is that there will be no correlation between temperature and respiration rate.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">Take the other empty container with a screw cap, the cup with your fish, and the net to the water tanks.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then, fill the empty container with the water from the lowest temperature water bath. This will act as your first respiration rate chamber.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Next, hold the fish net over a wastewater container and dump out the water from the cup holding the fish so that the fish falls into the net. Pinch the net around the fish without touching the fish itself.
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Bring the net over the top of the container with the bath water and let go of the net to release the fish into the vial.
</div></li><li data-sub-note-item="2-9"><div class="lab-step">Once the fish is in the container, submerge it back into the water bath and then screw the cap on to prevent outside oxygen from entering the vial.
</div></li><li data-sub-note-item="2-10"><div class="lab-step">Next, remove the container from the controlled temperature water bath and place it on your workbench surface to avoid warming the water with body heat.
</div></li><li data-sub-note-item="2-11"><div class="lab-step">One partner should immediately begin counting the gill beats as soon as the second partner starts the stopwatch.
</div></li><li data-sub-note-item="2-12"><div class="lab-step">Continue counting the beats for 20 seconds. Record the number of beats in column A of Table 2. <a href="https://www.jove.com/CDNSource/lm/labs/9/Table_2_Physiology_of_Circulatory_System.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 2</a>
</div></li><li data-sub-note-item="2-13"><div class="lab-step">Repeat the measurement one more time and record the number in column B.
</div></li><li data-sub-note-item="2-14"><div class="lab-step">Next, hold the fish net over a wastewater container and dump out the water from the fish vial so that the fish falls into the net.  IMPORTANT: Move from lowest to highest temperature, so the fish is not stressed between trials.
</div></li><li data-sub-note-item="2-15"><div class="lab-step">Repeat the experiment for the remaining four temperature conditions (steps 8 &#8211; 13).
</div></li><li data-sub-note-item="2-16"><div class="lab-step">Record all the values for different temperatures in Table 2.
</div></li><li data-sub-note-item="2-17"><div class="lab-step">Once you are done, slowly mix water from the last respiration chamber with the fish tank water and then return the fish to the home tank. NOTE: This should be done over the course of approximately 10 minutes.
</div></li></ul></li><li data-note-item="3" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="3-1"><div class="lab-step">It&#39;s time to analyze the data that you just collected. Look at the blood pressure and heart rate measurements for the different trials. If they were different, make a hypothesis to explain your observations. 
</div></li><li data-sub-note-item="3-2"><div class="lab-step">For the gill beat experiment, average the numbers in columns A and B and calculate the fish respiration rate as gill beats per minute.
</div></li><li data-sub-note-item="3-3"><div class="lab-step">Next, plot the graph of temperature versus gill beats per minute.
</div></li><li data-sub-note-item="3-4"><div class="lab-step">Record any correlations you see between the variables. If a correlation is observed, determine if it is positive or negative and provide an explanation for this result.  NOTE: Consider the fact that fishes are ectotherms and the impact of temperature on dissolved oxygen.
</div></li></ul></li></ol>