In which phase of meiosis does recombination occur?

Recombination, also known as crossing over, occurs during Prophase I of meiosis. During this phase, homologous chromosomes pair up tightly in a process called synapsis, forming structures known as tetrads. While paired, non-sister chromatids can exchange segments of genetic material. This genetic exchange is crucial for increasing genetic diversity in gametes produced during meiosis. Recombination leads to new combinations of alleles, contributing to the genetic variation observed in offspring.

In contrast, the other phases mentioned do not involve recombination. Metaphase I is the stage where the tetrads align at the cell's equatorial plane, Anaphase I is characterized by the separation of homologous chromosomes to opposite poles, and Telophase I is when the nuclear membranes may reform around the separated chromosomes, followed by cytokinesis. None of these phases involve the critical process of genetic recombination that occurs specifically in Prophase I.