During what phase of meiosis does crossing over occur?

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

Answer: (A)

Verified step by step guidance

1. Understand that meiosis is a type of cell division that reduces the chromosome number by half, creating four haploid cells. It consists of two stages: Meiosis I and Meiosis II.
2. Recognize that crossing over is a process where homologous chromosomes exchange genetic material. This increases genetic diversity in the resulting gametes.
3. Identify that crossing over occurs during Prophase I of Meiosis I. During this phase, homologous chromosomes pair up in a process called synapsis, forming structures known as tetrads.
4. Note that the physical exchange of chromosome segments between non-sister chromatids occurs at points called chiasmata during Prophase I.
5. Remember that the other phases listed (Anaphase I, Metaphase I, and Telophase I) involve different processes such as chromosome alignment, separation, and cell division, but not crossing over.