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Pachytene

Assertion A: ...

Question

Assertion (A): Events in pachytene play a key role in evolutionary changes in organisms
Reason (R): Exchange of genetic material takes place between sister chromatids of homologous chromosomes

A

A and R are true, R is correct explanation of A.

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B

Both A and R are true, R is not the correct explanation of A.

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C

A is true, R is false.

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D

A is false, It is true.

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Solution

The correct option is B A is true, R is false.
Crossing over is the process of the exchange of genetic material between non-sister chromatids of homologous chromosomes to produce new genetic combinations or variations. It occurs during pachytene of prophase I of meiosis I. These variations serve as raw material for evolution as natural selection acts upon them to produce new species. The assertion is correct. The reason is incorrect as cross over takes place between non-sister chromatids, not between sister chromatids of homologous chromosomes.
So, the correct option is 'C'.

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