Best description of the process of crossing over during meiosis:
- A. Duplication of chromosome
- B. Exchange of genes between non-sister chromatids
- C. Movement of chromosome to opposite poles
- D. Separation of sister chromatids
Explanation
During prophase I the homologues pair as bivalents and non sister chromatids exchange equal segments at chiasmata, producing chromosomes carrying combinations neither parent had. The exchange must be between non sister chromatids, since sister chromatids are identical and swapping between them would change nothing. Separation of sister chromatids happens later, in anaphase II.
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