Chromosome Count in Spermatogenesis — NEET Biology
✅ Asked in NEET 2026The primary sex organs – the testis in the males and the ovaries in the females – produce gametes, i.e, sperms and ovum, respectively, by the process called 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. The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids. What would be the number of chromosome in the spermatids? The spermatids are transformed into spermatozoa (sperms) by the process called spermiogenesis. After spermiogenesis, sperm heads become embedded in the Sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation.
NTA tests students' understanding of how chromosome numbers change through meiotic divisions in spermatogenesis. Starting from spermatogonia (46 chromosomes), primary spermatocytes undergo meiosis I to produce secondary spermatocytes (23 chromosomes each), which then divide in meiosis II to form spermatids (23 chromosomes each). Students commonly mistake spermatids for having 46 chromosomes or forget that meiosis II maintains the haploid number. The key to remember: after the first meiotic division, chromosome count is halved and remains halved through the second division. Every gamete must be haploid (23) to restore diploid number (46) upon fertilization.
This paragraph was tested 2 times in NEET.
About spermatogenesis: A. Spermatogonia always undergo meiotic division. B. Primary spermatocytes divide mitotically. C. Secondary spermatocytes form haploid spermatids via meiosis II. D. Spermatids form spermatozoa by mitosis. E. Spermatids transform into spermatozoa by spermiogenesis.
[NEET 2022 Phase 2] How many secondary spermatocytes are required to form 400 million spermatozoa?
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