question_answer

Directions : (16 - 20)

Read the passage given below and answer the following questions.

In testis, the immature male germ cells i.e., spermatogonia produce sperms by spermatogenesis that begins at puberty (13 to 16 years). Testosterone plays a significant role in puberty. The spermatogonia (sing. spermatogonium) present on the inside wall of seminiferous tubules multiply by mitotic division and increase in numbers. Each spermatogonium is diploid and contains 46 chromosomes. Some of the spermatogonia called primary spermatocytes periodically undergo meiosis. A primary spermatocyte completes the first meiotic division, i.e. reduction division leading to formation of two equal, haploid cells called secondary spermatocytes, which have only one set of chromosomes each. The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids. The spermatids are transformed into spermatozoa or sperms by the process called spermiogenesis. After spermiogenesis, sperm heads become embedded in the Sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation. Spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropin releasing hormone GnRH). It is a hypothalamic hormone. The increased levels of GnRH then acts at the anterior pituitary gland and stimulates secretion of two gonadotropins hormones: LH (Leuteinising Hormone) ; It acts at the Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the process of spermatogenesis. FSH (Follicle Stimulating Hormone) : It acts on the Sertoli cells and stimulates secretion of Androgen binding factors (ABP) which help in the process of spermiogenesis.

Spermatogenesis in human beings begins at the age of

A) 10 to 13 years

B) 13 to 16 years

C) 16 to 19 years

D) 19 to 21 years