Double-strand breaks (DSB) are needed for crossing-over to occur in meiosis. In a pair of homologous chromosomes, how many chromatids require a DSB in order for crossing over to occur?

Question

Quizplus · Accepted Answer

There are four chromatids in a pair of homologous chromosomes (each chromosome has two sister chromatids). One DSB is needed in one sister chromatid of one homologue. This then instigates a crossover with one of the chromatids of the other homologue.

Double-Strand Breaks (DSB) Are Needed for Crossing-Over to Occur in Meiosis