Crossing over between homologous chromosomes takes place during
Correct answer: C. prophase I
- A. metaphase I
- B. anaphase I
- C. prophase I
- D. telophase II
Explanation
During the pachytene stage of prophase I the homologues are paired as bivalents, and non sister chromatids exchange equal segments at points called chiasmata. Pairing must happen before the chromosomes line up on the spindle, so no later stage can allow the exchange. The chiasmata remain visible into metaphase I and hold the bivalent together.
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About Gene Linkage and Crossing Over
Linked genes lie on the same chromosome and tend to pass together, unlike genes that assort independently on different chromosomes. The topic connects linkage with homologous pairing, crossing over during prophase I of meiosis, recombinant and parental offspring, and recombination frequency as an estimate of gene distance.
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