Question

The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division malfunctions, and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following?A) Mitosis in ber ovary B) Metaphase I of one meiotic event C) Telophase II of one meiotic event D) Telophase I of one meiotic event E) Either anaphase I or II

Answer 1

Answer:

E) Either anaphase I or II

Explanation:

Failure of segregation of homologous chromosomes during anaphase I or failure of segregation of sister chromatids during anaphase II leads to the presence of the abnormal number of chromosomes in resultant gametes. In the given example, the egg mother cell with 48 chromosomes (24 pairs) would enter meiosis I but the failure of one pair of homologous chromosomes to segregate from each other followed by normal meiosis II would result in the formation of two gametes with one extra chromosome and two gametes with one less chromosome.

On the other hand, if the nondisjunction occurs at anaphase II of meiosis II, two normal gametes, one gamete with one extra chromosome and one gamete with one less chromosome will be formed. Therefore, nondisjunction at anaphase I or anaphase II would have resulted in the production of eggs with one extra chromosome.