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Chapitre 8

Transcription: de l'ADN à l'ARN

Qu’est-ce que l’expression génique ?
Qu’est-ce que l’expression génique ?
Overview Gene expression is the process in which DNA directs the synthesis of functional products, that is, proteins. Cells can regulate gene ...
Structure de l’ARN
Structure de l’ARN
Overview The basic structure of RNA consists of a five-carbon sugar and one of four nitrogenous bases. Although most RNA is single-stranded, it can form ...
Stabilité de l’ARN
Stabilité de l’ARN
Intact DNA strands can be found in fossils, while scientists sometimes struggle to keep RNA intact under laboratory conditions. The structural variations ...
ARN polymérase bactérienne
ARN polymérase bactérienne
Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. ...
Types d’ARN
Types d’ARN
Overview Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs ...
Transcription
Transcription
Overview Transcription is the process of synthesizing RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene ...
Facteurs de transcription
Facteurs de transcription
Tissue-specific transcription factors contribute to diverse cellular functions in mammals. For example, the gene for beta globin, a major component of ...
ARN polymérase eucaryote
ARN polymérase eucaryote
RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional ...
Régulation de l'initiation de la transcription
Régulation de l'initiation de la transcription
Proteins that regulate transcription can do so either via direct contact with RNA Polymerase or through indirect interactions facilitated by adaptors, ...
Facteurs d’élongation de la transcription
Facteurs d’élongation de la transcription
Transcription elongation is a dynamic process that alters depending upon the sequence heterogeneity of the DNA being transcribed. Hence, it is not ...
Transformation du pré-ARNm
Transformation du pré-ARNm
In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or ...
Épissage de l’ARN
Épissage de l’ARN
Splicing is the process by which eukaryotic RNA is edited before its translation into protein. The RNA strand transcribed from eukaryotic DNA is called ...
La structure de la chromatine régule la modification du pré-ARNm
La structure de la chromatine régule la modification du pré-ARNm
In eukaryotic cells, nascent mRNA transcripts need to undergo many post-transcriptional modifications to reach the cell cytoplasm and translate into ...
Transfert de l'ARNm hors du noyau
Transfert de l'ARNm hors du noyau
Before mRNAs are exported to the cytoplasm, it is crucial to check each mRNA for structural and functional integrity. Eukaryotic cells use several ...
Synthèse des ARN ribosomiques
Synthèse des ARN ribosomiques
Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal ...
Synthèse de l’ARN de transfert
Synthèse de l’ARN de transfert
One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the ...
Le nucléole
Le nucléole
The nucleolus is the most prominent substructure of the nucleus. When it was first discovered, it was considered to be an isolated organelle that forms ...
Corps nucléaires additionnels
Corps nucléaires additionnels
The eukaryotic nucleus is a double membrane-bound organelle that contains nearly all of the cell’s genetic material in the form of chromosomes. It ...
Épissage alternatif de l’ARN
Épissage alternatif de l’ARN
Alternative RNA splicing is the regulated splicing of exons and introns to produce different mature mRNAs from a single pre-mRNA. Unlike in constitutive ...
Transcription bactérienne
Transcription bactérienne
RNA polymerase (RNAP) carries out DNA-dependent RNA synthesis in both bacteria and eukaryotes. Bacteria do not have a membrane-bound nucleus. So, ...
Initiation de la transcription
Initiation de la transcription
Initiation is the first step of transcription in eukaryotes. Prokaryotic RNA Polymerase (RNAP) can bind to the template DNA and start transcribing. On the ...
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