The number of chromosomes present after first reductional division in each spermatocytes are:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 23
Each spermatogonium and each primary spermatocyte is diploid and has 46 chromosomes. The first meiotic division is the reduction division. It separates the two members of each chromosome pair, so the chromosome number is halved.
(1) 232 — Incorrect. The chromosome number is a plain count. A power of 23 has no meaning here.
(2) 46 — Incorrect. This is the number in the primary spermatocyte, before the first meiotic division. It does not stay the same after the division.
(3) 23 — Correct. A primary spermatocyte completes the first meiotic division and forms two haploid secondary spermatocytes. Each of them has only 23 chromosomes. The second meiotic division then gives four spermatids.
(4) 462 — Incorrect. This has no meaning as a chromosome number, and the number cannot rise after a reduction division.
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.”