Crossing-over occurs during prophase I of meiosis, specifically in the pachytene stage. During this stage, homologous chromosomes pair tightly in a process called synapsis, and non-sister chromatids exchange segments of genetic material. This exchange creates genetic variation by recombining alleles between homologous chromosomes. The sites of crossing-over are called chiasmata, which become visible in the subsequent diplotene stage
. To summarize:
- Crossing-over happens in prophase I of meiosis.
- More precisely, it occurs during the pachytene substage of prophase I.
- It involves the exchange of genetic material between non-sister chromatids of homologous chromosomes.
- This process increases genetic diversity in the resulting gametes
