alleryStart learning →Sister chromatids emerging from meiosis I are not perfectly identical because:
AAt least one crossover per chromosome occurs
BReplication copies each strand inaccurately
COne chromatid is always left unreplicated
DEach chromatid is built from a different parent
Answer & Solution
Correct answer: A. At least one crossover per chromosome occurs
1. Sister chromatids are merely duplicates of one of the two homologous chromosomes.
2. That would make them identical if nothing else happened.
3. Instead, they are different because there has always been at least one crossover per chromosome.
4. Crossing over swaps segments between homologues, so each sister ends up carrying a different mixture.
5. Replication itself is faithful, so copying error is not the explanation.
_Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 11 'Meiosis and Sexual Reproduction', sections 11.1-11.2_
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