Human Reproduction

The correct option is (A): Klinefelter’s Syndrome

Klinefelter’s Syndrome

1. Klinefelter's syndrome is a genetic condition characterized by an additional X chromosome -XXY on the sex chromosome.
2. Because of the additional X chromosome, estrogen secretion is high, resulting in sterility, but overall masculine development.

Explanation: Among the hormones listed in the options, androgen (a group of male hormones) is the hormone that is produced by the ovaries in females in very minimal amounts, but it is not produced by the placenta.
Meanwhile, other hormones like HCG (human chorionic gonadotropin), HPL (human placental lactogen), and estrogen are produced by the placenta.
Their roles in supporting pregnancy are as follows:

1. HCG: HCG or Human Chorionic Gonadotrophin, has several functions, such as helping to maintain the corpus luteum in the early stages of pregnancy, preventing menstruation by helping in progesterone production, & supporting fetal development. HGC test is usually done to detect pregnancy.
2. HPL: HPL or Human Placental Lactogen, helps to support pregnancy by, regulating maternal metabolism, stimulating the development of maternal breast tissue, redistributing nutrients from mother to fetus, decreasing maternal insulin sensitivity, and stimulating fetal growth.
3. Estrogen: Estrogen is one of the major hormones that control menstrual cycle as well as pregnancy. During pregnancy, it supports uterine growth and its proper blood flow, helps to develop fetal organs, and prepares the birth canal during parturition. It also helps to develop breast tissues & maintains overall pregnancy.

So, the correct option is (D) : androgens.

Spermatogenesis involves the creation of sperm in males, occurring within the seminiferous tubules located in the testes. During this process,
(a) Spermatogonia, located on the inner wall of the seminiferous tubules, undergo mitotic division, resulting in an increase in their numbers.
(b) Every spermatogonium is diploid, housing a total of 46 chromosomes.
(c) Spermatogonia that periodically undergo meiosis are termed primary spermatocytes.
(d) When a primary spermatocyte undergoes the first meiotic division, it results in the formation of two equal, haploid cells known as secondary spermatocytes, each containing only 23 chromosomes.
(e) Secondary spermatocytes proceed to undergo the second meiotic division, giving rise to four equal, haploid spermatids.
(f) Spermatids are transformed into spermatozoa (sperms) through the process known as spermiogenesis.
Now, let's see the diagram :

Hence, the correct sequence of spermatogenic stages culminating in the formation of sperm in a mature human testis is:
Spermatogonia - Primary spermatocytes - secondary spermatocytes - spermatids - spermatozoa
So, the correct option is (D) : (D), (E), (A), (B), (C).

(A) - (III), (B) - (IV), (C) - (I), (D) - (II)

To understand the correct order of the stages of oogenesis, we should first define each stage:

• Oogonia (B): These are the initial germ cells in the ovaries, which proliferate by mitosis during fetal development.
• Primary oocyte (C): Oogonia develop into primary oocytes that initiate meiosis but halt at prophase I until puberty.
• Secondary oocyte (D): Upon maturation and ovulation, some primary oocytes resume meiosis and form secondary oocytes. This stage is arrested in metaphase II unless fertilization occurs.
• Ovum (A): The final mature egg cell, formed only if the secondary oocyte completes meiosis II after fertilization.

Following the natural biological progression, the correct sequence of stages during oogenesis is:

1. Oogonia (B)
2. Primary oocyte (C)
3. Secondary oocyte (D)
4. Ovum (A)

Therefore, the correct answer is: (B), (C), (D), (A)

In humans, the determination of an embryo's sex occurs at fertilization when the genetic material from the egg and sperm combine. The eggs produced by a female always contain an X chromosome. In contrast, a male's sperm can contain either an X or a Y chromosome. This means:

• If a sperm carrying an X chromosome fertilizes the egg, the resulting zygote will have two X chromosomes (XX), resulting in a female embryo.
• If a sperm carrying a Y chromosome fertilizes the egg, the zygote will have one X and one Y chromosome (XY), resulting in a male embryo.

Therefore, the sex of the human embryo is determined by whether the fertilizing sperm carries an X or a Y chromosome.