Crossing over in prophase I
When does crossing over between homologous chromosomes occur?
Answer A: explanation for every choice
A
Correct. Homologs pair as tetrads during prophase I, and crossing over occurs there.
B
Metaphase II lines up sister chromatids. Homologs have already separated.
C
Mitosis does not pair homologs, so crossing over does not normally occur.
D
Homologs are already in separate cells by prophase II.
TakeawaySynapsis and crossing over: prophase I.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb80.