Q.Observe the diagram, and answer the questions:
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Start your 14-day free trial to unlock the full solution →The tubule wall-to-lumen sequence is spermatogonia (B) → primary spermatocyte (C) → secondary spermatocyte (D) → spermatid (E) → spermatozoon (A); reduction division happens in C.
Inside a seminiferous tubule, spermatogenesis proceeds in a fixed spatial order from the basement membrane (tubule wall) toward the lumen, so the labels read bottom-to-top as the cells mature:
- B (bottom-most, against the wall) = Spermatogonia — diploid (2n) germ cells that multiply by mitosis and act as the stem-cell population.
- C = Primary spermatocytes — formed when spermatogonia enlarge (grow in size, accumulate cytoplasm) and commit to meiosis; still diploid (2n).
- D = Secondary spermatocytes — haploid (n) cells produced when a primary spermatocyte completes meiosis I.
- E = Spermatids — haploid (n) cells produced when a secondary spermatocyte completes meiosis II.
- A (top-most, tailed) = Spermatozoa — formed from spermatids by spermiogenesis (loss of cytoplasm, formation of the acrosome and flagellum), then released into the lumen by spermiation.
a) Identify A and B: A = spermatozoa (mature sperm cells with a flagellum/tail); B = spermatogonia (the germinal cells lying nearest the tubule's basement membrane).
b) Function of C: C, the primary spermatocyte, is the cell that actually carries out the first meiotic (reduction) division — it divides to produce two secondary spermatocytes (D), each with half the chromosome number of the primary spermatocyte.
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