In meiosis, at which phase do homologous chromosomes separate?

• A. Metaphase I
• B. Anaphase I
• C. Anaphase II
• D. Prophase I

Answer: (B)

Homologous chromosomes separate during Anaphase I. After they pair up and form tetrads in Prophase I, and then align as homologous pairs during Metaphase I, the homologues are pulled to opposite poles in Anaphase I. This separation happens because cohesin holding the arm regions of the homologues together is cleaved, freeing the homologous chromosomes while sister chromatids remain attached at the centromeres. The sister chromatids only separate later, in Anaphase II, once the centromeric cohesin is cleaved. Prophase I involves pairing and crossing over, not the separation of homologs.