Optometry Admission Test (OAT) Practice 2025 - Free Optometry Admission Test Practice Questions and Study Guide

Crossing over occurs during Prophase I of meiosis. This is a crucial event in genetic recombination where homologous chromosomes pair up and exchange segments of their chromatids. In Prophase I, the chromosomes condense, and homologous chromosomes undergo synapsis, forming structures called tetrads. This close pairing allows for the exchange of genetic material, which increases genetic diversity in the resulting gametes.

This process is an essential feature of meiosis that differentiates it from mitosis, where crossing over does not occur. The other phases listed, such as Prophase II, Metaphase I, and Anaphase I, do not involve crossing over; Prophase II focuses on the preparation for the second meiotic division without homologous pairing, Metaphase I is when chromosomes align at the cell's equator, and Anaphase I involves the separation of homologous chromosomes without crossover events.