Spermatogenesis in mammals involves both mitosis and meiosis. Type AS spermatogonia can undergo mitosis to form type Al spermatogonia, which in turn undergo mitosis to form type B spermatogonia. Type B spermatogonia undergo a final round of mitosis to form primary spermatocytes. Primary spermatocytes undergo the first meiotic division to make secondary spermatocytes, and these undergo the second meiotic division to form spermatids. Spermatids then enters spermiogenesis to form sperm. If the spermatids have a ploidy of 1n and are haploid, which cells would have a ploidy of 4n?
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a
Type AS spermatogonia
b
Type Al spermatogonia
c
Type B spermatogonia
d
Primary spermatocytes
e
Secondary spermatocytes
d. Primary spermatocytes
The cells that would have a ploidy of 4n are d) Primary spermatocytes.
The correct answer is d) Primary spermatocytes.
To determine which cells would have a ploidy of 4n, we need to identify the stage of meiosis where the chromosome number is doubled.
Type AS spermatogonia, Type Al spermatogonia, and Type B spermatogonia all undergo mitosis, which results in cells with the same ploidy as the parent cell (2n).
Primary spermatocytes, on the other hand, undergo the first meiotic division (meiosis I). Meiosis I is where the chromosome number is halved, resulting in cells with a ploidy of 1n (haploid). However, these primary spermatocytes are still diploid (2n) at this stage because they have replicated their DNA during the previous S phase. Therefore, primary spermatocytes have a ploidy of 4n.
Secondary spermatocytes, which are formed after the first meiotic division, would have a ploidy of 2n. Spermatids, the final product of spermatogenesis, have a ploidy of 1n, as they have undergone the second meiotic division.
So, the cells that would have a ploidy of 4n are the primary spermatocytes.