Which structures indicate where crossing over has occurred during meiosis?

• A. Spindle fibers
• B. Chiasmata
• C. Nucleoli
• D. Centromeres

Answer: (B)

Verified step by step guidance

1. Understand the process of meiosis: 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. Learn about crossing over: Crossing over is a process that occurs during prophase I of meiosis I, where homologous chromosomes exchange genetic material. This increases genetic diversity.
3. Identify the structures involved in crossing over: During crossing over, homologous chromosomes pair up and form structures called tetrads. The points where the chromosomes physically exchange segments are known as chiasmata.
4. Recognize the role of chiasmata: Chiasmata are the visible manifestations of crossing over. They appear as X-shaped structures where the chromatids have exchanged genetic material.
5. Differentiate chiasmata from other structures: While spindle fibers, nucleoli, and centromeres are important in cell division, they do not indicate crossing over. Chiasmata specifically mark the sites of genetic exchange during meiosis.