Question

What are spermatogonia, primary spermatocytes and secondary spermatocytes?

Hint:

Exam line: \textbf{Meiosis I} makes the cell \emph{haploid}; \textbf{Meiosis II} halves the DNA per chromosome. Bas is sequence ko yaad rakho.

Answer 1

Step 1: Spermatogonia (2n).
Basal lamina par seminiferous tubules ke andar paaye jaane wale mitotically active stem cells hote hain.
Type A (stem pool maintain karte) aur Type B (meiotic pathway par commit) milte hain. Sab diploid (2n) hote hain.
Step 2: Primary spermatocytes (2n, 4C DNA).
Type B spermatogonia ke growth \& S-phase ke baad bante hain. Inka chromosome number diploid (2n) rehta hai par DNA content duplicate ho kar 4C ho jata hai.
Yeh blood–testis barrier cross karke adluminal compartment me enter karte hain aur Meiosis I start karte hain.
Step 3: Secondary spermatocytes (n, 2C DNA).
Primary spermatocyte ke Meiosis I complete karne par bane cells hain. Chromosome number haploid (n) hota hai, lekin har chromosome abhi do chromatids wala hota hai (2C DNA).
Yeh short-lived hote hain aur turant Meiosis II karke haploid spermatids (n, 1C) banate hain.
Step 4: Flow yaad rakho.
Spermatogonia (2n) $\rightarrow$ Primary spermatocyte (2n, 4C) $\rightarrow$ Secondary spermatocyte (n, 2C) $\rightarrow$ Spermatid (n, 1C) $\rightarrow$ Spermatozoa.