Biology 30 – Mitosis and Meiosis Practice Test 2026 - Free Mitosis and Meiosis Practice Questions and Study Guide

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Explain crossing over and its consequences for genetic variation.

Exchange of genetic material between non-sister chromatids at chiasmata during prophase I, creating recombinant chromatids and increasing genetic diversity.

Crossing over occurs during prophase I of meiosis when homologous chromosomes pair up and non-sister chromatids exchange segments at the sites called chiasmata. This shuffling creates recombinant chromatids that carry a mix of maternal and paternal alleles. When gametes are formed, these new allele combinations increase genetic variation among offspring, providing more diverse material for natural selection to act on. It’s important to note that this exchange happens between non-sister chromatids of homologous chromosomes, not between sister chromatids, and it does not occur during mitosis or at metaphase II.

Exchange between sister chromatids during metaphase II.

No genetic change occurs.

It occurs during mitosis.