question_answer 32)

  Which among the following has 23chromosomes? (a) Spermatogonia          (b) Zygote                           (c) Secondary oocyte     (d) Oogonia

Answer:

                  (c) Secondary oocyte has 23 chromosomes as it is a product of meiotic division of primary oocyte during oogenesis in the ovary. Oogenesis is initiated at the foetal ovary in the early embryonic stage of female and a fixed number of oogonia (gamete mother cells) are formed at before the birth of the female child no more oogonia are added after birth. Spermatogonia is the immature male germ cells that produce sperms. Each spermatogonium is diploid (2n) and contain 46 chromosomes.The haploid nucleus of the sperms and that of the ovum fuse together to form a diploid(2n) zygote i.e., 46 chromosomes. During foetal development, certain cells in the germinal epithelium of the ovary undergo mitotic divisions, producing undifferentiated germ cells called oogonia. The oogonia is diploid (2n) and contains 46 chromosomes.