Question

Human females possess 44+ XX chromosomes. The secondary oocyte shall have
A. 44+XX
B. 22+X
C. 22
D. 44

Answer 1

Hint: In humans, there are 23 pairs of chromosomes out of which 22 pairs are autosomes and one pair are allosomes or sex chromosomes. In male, X and Y sex chromosomes are present. In females , two X chromosomes are present. The question is about secondary oocytes. In order to answer this question, let us know about oogenesis. It is the process of maturation of ovum.

Complete answer:
The process of oogenesis which takes place inside a female before giving birth to an offspring. The female reproductive system releases female gametes called eggs. Before birth, the primary oocyte is formed from oogonium and is diploid. As it is diploid, it contains 44+XX chromosomes. The primary oocyte undergoes meiosis and forms two haploid cells of unequal sizes. One of the daughter cells which receives less cytoplasm, becomes a polar body and the other daughter cell is a secondary oocyte. Here, the polar body divides to form two other polar bodies whereas the secondary oocyte is paused in the metaphase stage of meiosis II. As this secondary oocyte is formed as a result of meiosis, it is haploid and hence contains half the number of parent chromosomes.

Hence it is said to have 22+X chromosomes. The correct answer is option B.

Note:
The secondary oocyte which was arrested at metaphase stage of meiosis II, completes the division during fertilization. If the fertilization does not occur, it gets degenerated within 24 hours. The process where the secondary oocyte is released from the ovary is called ovulation whereas in male it is called spermatogenesis.