In what stage of meiosis does crossing over occur?

• A. Prophase I
• B. Metaphase I
• C. Anaphase 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 stage, 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 crossing over is a key event in Prophase I, distinguishing it from other stages like Metaphase I, Anaphase I, and Telophase I, where different processes occur.