Question

Segregation of Mendelian factor (Aa) occurs during

• A. diplotene
• B. anaphase I
• C. zygotene/pachytene
• D. anaphase II.

Answer 1

The Correct Option is B

To address the question about the segregation of Mendelian factors, we need to understand the processes involved in meiosis, which is a type of cell division that reduces the number of chromosomes by half and produces gametes or spores. The question specifically asks about when the segregation of a Mendelian factor, represented as Aa, occurs.

During meiosis, two consecutive divisions occur: Meiosis I and Meiosis II, each having its own stages such as prophase, metaphase, anaphase, and telophase. Mendelian segregation corresponds to the separation of allele pairs.

Explanation:

1. Anaphase I: This is the stage during Meiosis I where homologous chromosomes are separated. At this point, the pair of alleles for a gene are segregated into different cells. For instance, if a diploid cell has chromosomes with alleles Aa, during anaphase I, each resulting cell receives one chromosome, thereby separating the alleles A and a.
2. Diplotene: In this stage of prophase I, homologous chromosomes start to separate apart, and chiasmata become visible. However, the actual segregation of alleles does not occur here.
3. Zygotene/Pachytene: Both are earlier stages of prophase I, where synapsis occurs, but no segregation of alleles takes place.
4. Anaphase II: This stage belongs to Meiosis II, where sister chromatids are pulled apart. It is not the point where alleles segregate; instead, it is a separation of duplicated chromosomes.

Thus, the correct answer is anaphase I, as this is the stage during which homologous chromosomes and their respective alleles are segregated into different cells.