Step 1: Understanding the Concept:
Spermatogenesis is the sequence of cellular divisions and transformations by which male primordial germ cells develop into mature, motile spermatozoa within the seminiferous tubules of the testes. It relies on a precise combination of regular mitosis and two subsequent stages of reductionist meiosis.
Step 2: Detailed Explanation:
Let's analyze the accuracy of each given statement:
- Statement A is incorrect: Spermatogonia are diploid stem cells ($2n = 46$). They do not always undergo meiosis. Many undergo mitotic cell division to maintain the stem cell population so that sperm production can continue throughout adult life.
- Statement B is incorrect: Primary spermatocytes ($2n$) are the specific cells that initiate the reduction division pathway. They divide by meiotic cell division (Meiosis I)—not mitosis—to produce two haploid secondary spermatocytes.
- Statement C is correct: Because Meiosis I separates homologous chromosome pairs, the resulting secondary spermatocytes are fully haploid, meaning they contain exactly 23 chromosomes. These haploid cells promptly undergo Meiosis II (the second meiotic division) to generate four spermatids.
- Statement D is incorrect: This states the sequence backward. Non-motile, spherical spermatids are transformed into mature, elongated, motile spermatozoa through a specialization process called spermiogenesis.
Since statement C is the only scientifically accurate claim, option (B) is our correct choice.
Step 3: Final Answer:
The only correct statement is C, making the correct option (B).