In spermatogenesis, the phase of maturation involves formation of spermatids from primary spermatocytes through meiosis...

The correct answer is option 'D', which states that the phase of maturation in spermatogenesis involves the formation of spermatids from primary spermatocytes through meiosis. Let's break down the process of spermatogenesis and understand why this is the correct answer.

Spermatogenesis is the process by which male germ cells, called spermatogonia, undergo a series of complex changes to develop into mature spermatozoa or sperm cells. It occurs in the seminiferous tubules of the testes.

The process of spermatogenesis can be divided into three main phases: the proliferative phase, the meiotic phase, and the differentiation phase. The phase of maturation refers to the differentiation phase, where spermatids are formed from primary spermatocytes through meiosis.

Here is a detailed explanation of the process:

1. Proliferative Phase:
- Spermatogonia, the diploid germ cells, undergo mitotic divisions to increase their number.
- Some spermatogonia remain as reserve stem cells, while others differentiate into primary spermatocytes.

2. Meiotic Phase:
- Primary spermatocytes undergo meiosis I, resulting in the formation of two haploid secondary spermatocytes.
- Each secondary spermatocyte then undergoes meiosis II, resulting in the formation of four haploid spermatids.

3. Differentiation Phase (Maturation):
- Spermatids, which are round haploid cells, undergo a series of morphological changes to develop into mature spermatozoa.
- These changes include the condensation of chromatin, the formation of a flagellum for motility, and the development of an acrosome (a cap-like structure) for fertilization.

During this phase, the spermatids undergo extensive remodeling and elongation to form mature spermatozoa. This process is known as spermiogenesis. The mature spermatozoa are released into the lumen of the seminiferous tubules, where they are transported to the epididymis for further maturation and storage.

In summary, option 'D' is the correct answer because the phase of maturation in spermatogenesis involves the formation of spermatids from primary spermatocytes through meiosis. This process is essential for the production of functional sperm cells capable of fertilizing an egg.