Question

Which among the following has 23 chromosomes?
A. Spermatogonia
B. Zygote
C. Secondary oocyte
D. Oogonia

Answer 1

Hint: Meiosis I is a reductional division that reduces the number of chromosomes in primary oocyte and primary spermatocytes. Then, it leads to the formation of secondary oocytes and secondary spermatocytes.

Complete answer: Spermatogenesis is a process for the production of sperms from spermatogonia or male germ cells at puberty. Large numbers of spermatogonia are produced by multiple mitotic divisions of primary or primordial germ cells. Some spermatogonia stop dividing at sexual maturity of the individual and start accumulating cytoplasm and replicating DNA. These are termed as primary spermatocytes (diploid). Each diploid primary spermatocyte undergoes multiple divisions. The first reduction or meiotic division results in the formation of two haploid secondary spermatocytes. Secondary spermatocytes further undergo an equational division (mitotic division) to form four equal haploid spermatids. The process by which spermatids transform into spermatozoa (sperms) is termed spermiogenesis. In the female reproductive system, oogenesis is the process in which the primary egg cell develops into a mature ovum. The diploid egg cell increases in size and transforms into a primary oocyte. The secondary oocyte is produced by the reductional division or meiosis I of the primary oocyte. It has 23 chromosomes.

Hence, the correct option is C-Secondary oocyte.

Note: The spermatogenesis and oogenesis are the processes of the formation of male gametes and female gametes. Spermatogenesis releases four haploid motile male gametes and oogenesis releases a single haploid non-motile ovum from an oogonium.