Read the paragraph and answer the Question given below:
Humans are sexually reproducing and viviparous. The male reproductive system is composed of a pair of testes the male sex accessory ducts and the accessory glands and external genitalia. The female reproductive system consists of a pair of ovaries a pair of oviducts, a uterus, a vagina, external genitalia and pair of mammary glands. The reproductive cycle of female primates is called menstrual cycle. Menstrual cycle starts only after attaining sexual maturation (puberty). Coitus followed by fertilization leads to formation of zygote. After 9 months of pregnancy, the fully developed foetus is ready for delivery.
How many chromosomes are present in human primary spermatocytes?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 46
Option (1) 46 — Correct. Primary spermatocytes are spermatogonia that are about to enter meiosis. They have not divided yet, so they are still diploid, 2n = 46.
Option (2) 23 — Incorrect. 23 is the haploid number. It is found only after the first meiotic division, in the secondary spermatocytes, and then in the spermatids and sperms.
Option (3) 92 — Incorrect. 92 would be double the diploid number. No cell of spermatogenesis has 92 chromosomes; the DNA doubles before meiosis, but the chromosome number stays 46.
Option (4) 12 — Incorrect. 12 is not a chromosome number of any human cell. Human cells are either diploid (46) or haploid (23).
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Gametogenesis – “… In testis, the immature male germ cells (spermatogonia) produce sperms by spermatogenesis that begins at puberty. The spermatogonia (sing. spermatogonium) present on the inside wall of seminiferous tubules multiply by mitotic division and increase in numbers. 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.”