Assertion (A): Spermatogenesis starts at the age of puberty.
Reason (R): There is a significant increase in the level of gonadotropin-releasing hormone at puberty.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both Assertion (A) and Reason (R) are correct and R is the correct explanation of A.
Assertion (A): Spermatogenesis starts at the age of puberty. — True. A is about when sperm formation begins. The spermatogonia in the testis start producing sperms at puberty.
Reason (R): There is a significant increase in the level of gonadotropin-releasing hormone at puberty. — True. R is about a hormonal change at puberty. The secretion of GnRH (gonadotropin releasing hormone), a hypothalamic hormone, rises sharply at this age.
Why R explains A? GnRH acts on the anterior pituitary and makes it secrete LH (luteinising hormone) and FSH (follicle stimulating hormone). LH makes the Leydig cells secrete androgens, which stimulate spermatogenesis, and FSH acts on the Sertoli cells to help spermiogenesis. So the rise of GnRH at puberty is the cause of spermatogenesis starting at that age, and R is the correct explanation of A.
NCERT Extract:
Gametogenesis – “… Spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropin releasing hormone (GnRH). This, if you recall, is a hypothalamic hormone. The increased levels of GnRH then acts at the anterior pituitary gland and stimulates secretion of two gonadotropins – luteinising hormone (LH) and follicle stimulating hormone (FSH). LH acts at the Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the process of spermatogenesis.”