Which of the following statements are not correct?
A. A primary spermatocyte completes the first meiotic division to form two haploid cells called spermatogonia.
B. The secondary spermatocytes undergo the second meiotic division to produce four haploid spermatids.
C. Each oogonium is haploid and contains 23 chromosomes.
D. Oogenesis is initiated during the embryonic development stage.
E. The haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) and (C) only
A. A primary spermatocyte completes the first meiotic division to form two haploid cells called spermatogonia. — False. The first meiotic division gives two secondary spermatocytes. Spermatogonia are the diploid cells that come before the primary spermatocyte.
B. The secondary spermatocytes undergo the second meiotic division to produce four haploid spermatids. — True. The second meiotic division gives four equal, haploid spermatids.
C. Each oogonium is haploid and contains 23 chromosomes. — False. Oogonia are the gamete mother cells. Like spermatogonia, they are diploid, with 46 chromosomes. Only after meiosis do the cells become haploid.
D. Oogenesis is initiated during the embryonic development stage. — True. Oogonia are formed in the fetal ovary, and no more are added after birth.
E. The haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote. — True. This fusion at fertilisation restores the diploid number in the zygote.
So the statements that are not correct are A and C.
NCERT Extract:
Gametogenesis – “… Each spermatogonium is diploid and contains 46 chromosomes. Some of the spermatogonia called primary spermatocytes periodically undergo meiosis. A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocytes, which have only 23 chromosomes each. The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids (Figure 2.5). … Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each fetal ovary; no more oogonia are formed and added after birth.”
Fertilisation and Implantation – “… Soon the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote.”