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 processes?
telophase i of one meiotic event
telophase ii of one meiotic event
either anaphase i or ii of meiosis
mitosis in her ovary

Explanation:

• Anaphase I: Homologous chromosomes fail to separate properly. If this occurs, one daughter cell will have an extra chromosome (and the other will be missing one). When this cell proceeds through meiosis II, the resulting gametes (eggs in this case) can have an abnormal chromosome number.
• Anaphase II: Sister chromatids fail to separate. Similar to anaphase I error, if sister chromatids do not separate at anaphase II, one of the resulting gametes will have an extra chromosome.
• Telophase I and II: These are stages of cytokinesis (cell - splitting) and nuclear re - formation. Errors in telophase do not directly cause an extra chromosome in the gamete in the way described (an extra chromosome is due to improper chromosome separation, which occurs in anaphase).
• Mitosis in the ovary: Mitosis in the ovary is for the growth and maintenance of ovarian tissue (producing somatic cells like granulosa cells, theca cells etc.). Gametes (eggs) are produced by meiosis, not mitosis. So a mitotic error in the ovary would not lead to an egg with an extra chromosome.

Answer:

C. either anaphase I or II of meiosis