Gametogenesis - NEET Biology Class 12 Free MCQ Test with solutions

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 (reduction division) leading to formation of two equal, haploid cells called secondary spermatocytes, which have only 23 chromosomes each. The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid spermatids.

During gametogenesis, the cell that is normally diploid is: Spermatogonia
- Spermatogonia are the diploid cells in the testes that undergo mitosis to produce more spermatogonia or differentiate into primary spermatocytes.
- They are the germ cells that give rise to sperm cells through the process of spermatogenesis.
Therefore, the correct answer is C: Spermatogonia.

The correct answer is B: Sertoli cells.
- Sertoli cells:
- Located in the seminiferous tubules of the testes.
- Provide support and nutrition to developing male germ cells (spermatogonia) through various stages of spermatogenesis.
- Create a blood-testis barrier, protecting germ cells from harmful substances.
- Secrete growth factors and hormones essential for germ cell development and maturation.

These functions make Sertoli cells crucial for the proper development and nourishment of male germ cells.

The correct sequence of spermatogenetic stages leading to the formation of sperms in a mature human testis is:
- Spermatogonia
- Spermatocyte
- Spermatid
- Sperms
- Spermatogonia are the undifferentiated cells in the testes.
- Spermatogonia undergo mitosis to form primary spermatocytes.
- Primary spermatocytes undergo meiosis to form secondary spermatocytes which further differentiate into spermatids.
- Spermatids mature into sperm cells through the process of spermiogenesis.

Spermatogenesis commences in males at puberty due to a significant increase in the secretion of gonadotropin releasing hormone (GnRH). GnRH acts on the anterior pituitary gland, leading to the secretion of luteinising hormone (LH) and follicle stimulating hormone (FSH). LH stimulates the Leydig cells to produce androgens, which then stimulate spermatogenesis. FSH, on the other hand, acts on the Sertoli cells to facilitate the process of spermiogenesis.

Haploid cells are those containing a single set of chromosomes (n).

• Secondary spermatocytes are haploid cells formed after meiosis I.

• The first polar body is haploid and formed during oogenesis.

• Ovum is a haploid female gamete formed after completion of meiosis II.
  Therefore, the correct group of haploid cells is option B.

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Hence, the Correct Answer is B

NCERT Reference: Topic “Gametogenesis” and “Fertilisation and implantation” of chapter: Human Reproduction of NCERT.

The correct similarity between oogenesis and spermatogenesis is that both occur inside the primary sex organs:
-Oogenesis occurs in the ovaries (female primary sex organ).
-Spermatogenesis occurs in the testes (male primary sex organ).
Other options are incorrect:
The growth phase in oogenesis is prolonged and starts before birth, but in spermatogenesis, it starts at puberty.
Oogenesis produces non-motile ova, while spermatogenesis produces motile sperm.
Oogenesis typically produces one viable gamete per cycle, while spermatogenesis produces millions of sperm continuously.
Thus, the correct answer is Option D.

The process you're asking about occurs during oogenesis, which is the formation of egg cells (ova) in females. Here's how it works:

1. Primary Oocyte: The primary oocyte is a diploid cell, meaning it has two sets of chromosomes (2n). This cell begins the first meiotic division.

2. First Meiotic Division: During the first meiotic division, the primary oocyte divides unevenly. This asymmetrical division results in two cells:

   • Secondary Oocyte: This is the larger cell, and it contains most of the cytoplasm from the original primary oocyte. It is haploid, meaning it has only one set of chromosomes (n).
   • First Polar Body: This is the smaller cell, which also has a haploid set of chromosomes (n) but very little cytoplasm. The polar body is generally considered non-functional and may eventually degenerate.

3. Reason for Unequal Division: The unequal division ensures that the secondary oocyte retains enough cytoplasm and organelles to support early development if fertilization occurs. The polar body, being smaller and less resourced, is a byproduct of this process.

If fertilization occurs, the secondary oocyte will undergo a second meiotic division to form the mature ovum and another polar body. However, only one functional egg cell is produced from the original primary oocyte.

This process ensures that the resulting egg has enough nutrients and cellular machinery to support the early stages of embryonic development.