During which phase of meiosis does crossing over occur?

Crossing over occurs during Prophase I of meiosis. This is a crucial event in the process of genetic recombination, which enhances genetic variation in sexually reproducing organisms. During Prophase I, homologous chromosomes come together and pair up in a process called synapsis. While in this paired state, sections of chromatids can break and swap places, leading to new combinations of alleles. This genetic exchange not only contributes to diversity in gametes but also plays a key role in the evolutionary process by creating individuals with unique genetic profiles.

The other phases listed do not involve crossing over. For example, in Metaphase II, chromosomes align at the cell equator, and during Telophase I and Anaphase II, the process involves the separation of chromosomes or chromatids rather than any exchange of genetic material. Understanding this is essential for grasping how meiosis contributes to genetic variation in offspring.