Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to allelic diversity in the newly formed daughter cells. In humans, crossing over produces genetically distinct haploid egg and sperm cells that undergo fertilization to produce unique offspring. Before cell division starts, the germ cell’s chromosome(s) undergo duplication in the S phase of the cell cycle. As the cells enter prophase I, duplicated chromosomes condense and form two sister chromatids (identical copies of the original chromosome) joined by the centromere. Next, the homologous chromosomes pair up and align the same gene segment from the maternal and paternal chromosomes, forming a synapse. A protein complex called the synaptonemal complex is formed that holds these homologs together. As crossing over proceeds, random pieces of DNA are swapped between the homologs, producing new combinations of alleles via homologous recombination. The 'chiasmata' mark the areas where the crossover of genetic information has occurred. As the synaptonemal complex begins to dissolve, the chiasma holds the homologous chromosomes together until recombination is completed and chromosomes are segregated correctly into the daughter cells.

Tags
Crossing OverGenetic InformationHomologous ChromosomesProphase IMeiosis IGenetic RecombinationAllelic DiversityHaploid CellsFertilizationGerm Cell DuplicationSister ChromatidsSynapseSynaptonemal ComplexHomologous RecombinationChiasmataChromosome Segregation

来自章节 36:

article

Now Playing

36.5 : Crossing Over

Meiosis

3.6K Views

article

36.1 : 什么是减数分裂?

Meiosis

3.7K Views

article

36.2 : 减数分裂 I

Meiosis

12.5K Views

article

36.3 : 减数分裂 II

Meiosis

2.0K Views

article

36.4 : 减数分裂 vs. 有丝分裂

Meiosis

4.9K Views

article

36.6 : 非析取

Meiosis

3.4K Views

JoVE Logo

政策

使用条款

隐私

科研

教育

关于 JoVE

版权所属 © 2025 MyJoVE 公司版权所有,本公司不涉及任何医疗业务和医疗服务。