Gametogenesis
A. Gynosperms are male gametes
B. Primary oocytes are released at ovulation
C. Spermatozoa contain 23 chromosomes
D. Male gametes are two types
ANSWER- B.
B. Primary oocytes are released at ovulation
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The female gametes are secondary oocytes, which are released from the ovary in a cyclic fashion throughout the reproductive life of a female. chromosomes. In females, secondary oocytes are of only one type, i.e., each secondary oocyte has 22 autosomes and one X chromosome (22X).
In males, there are two types of sperms—one containing X (22X) and the other containing Y (22Y). The sperm containing X chromosomes is called X-bearing sperm or gynosperm and sperm containing Y chromosomes is called Y-bearing sperm or androsperm.
A. The period between the two mitotic divisions is called interphase.
B. Before mitosis begins, each chromosome replicates its deoxyribonucleic acid (DNA).
C. During interphase chromosomes are in the form of condensed ball
D. Nucleolus disappears in prophase
ANSWER- C.
C. During interphase chromosomes are in the form of condensed ball
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Ans. C
During interphase the chromosomes are in the form of long and thin threads (chromatin threads), which spread diffusely within the nucleus. They cannot be recognized with a light microscope at this stage. Later in prometaphase the chromatids become distinguishable and the nucleolus reappears in Telophase.
A. Synapsis of chromosomes and appearance of bivalents occur in the zygotene stage .
B. Leptotene is the longest stage which may extend for years
C. Exchange of genetic material occurs in diplotene phase
D. DNA does not duplicate in the second meiotic division.
ANSWER- C.
C. Exchange of genetic material occurs in diplotene phase
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Ans. C
Pachytene is the longest phase and may extend even for years. Formation of tetrahed and crossing over to form chiasmata occurs in this stage.
The second meiotic division is essentially similar to mitosis. It, however, differs from mitosis in that the DNA does not duplicate.
A. Synapsis of chromosomes and appearance of bivalents occur in the zygotene stage .
B. Leptotene is the longest stage which may extend for years
C. Exchange of genetic material occurs in diplotene phase
D. DNA does not duplicate in the second meiotic division.
ANSWER- A.
A. Synapsis of chromosomes and appearance of bivalents occur in the zygotene stage .
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Ans. A
At puberty, primordial germ cells undergo a series of divisions to form spermatogonia which stay in the walls of the seminiferous tubules of the testis.
Two types of spermatogonia are formed – Dark A type which are kept in reserve for repetition in the next cycle and light type A which undergoes mitotic division to form two dark type B spermatogonia. Primary spermatocytes are produced from dark type B spermatogonia. Up to this stage they have a diploid number of chromosomes. Later the primary spermatocyte undergoes meiotic division to give rise to haploid secondary spermatocytes.
A. Tail forms three-fifths of the length.
B. Mitochondria forms the axial sheath
C. End piece contains only axial filament
D. Axial filament and annulus both arise from centriole.
ANSWER- A.
A. Tail forms three-fifths of the length of spermatozoa.
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Ans. A
Tail forms Four-fifths of the length of spermatozoa.
Centrosome divides into two centrioles.
One centriole becomes spherical and moves towards the posterior end of the nucleus to occupy the neck region. It gives rise to the axial filament.
The other centriole moves away from the first centriole and becomes ring shaped. It forms an annulus/ring around the distal end of the middle piece
A. The primary oocyte is in the prophase of first meiotic division at birth.
B. The first meiotic division is unequal forming secondary oocyte and polar body
C. Second meiotic division is equal division which occurs at ovulation
D. One primary oocyte forms only one ovum with 22 autosomes and one X chromosome; and three polar bodies.
ANSWER- C.
C. Second meiotic division is equal division which occurs at ovulation
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Ans. C
The secondary oocyte enters the second meiotic division at ovulation, but gets completed at fertilization. The second meiotic division is also unequal so that one daughter cell forms the ovum, while the other forms the second polar body.
A. spermatogonium
B. primary spermatocytes
C. secondary spermatocyte
D. sustentacular cell
ANSWER- C.
C. secondary spermatocyte
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Ans. C
Secondary spermatocytes are haploid cells.
These cells rapidly undergo the second meiotic division and within 8 hours give rise to two spermatids.
In-Shorts
– Mitochondria forms the spiral axial sheath present in the middle piece.
– End piece contains only axial filament
– Golgi apparatus forms the acrosomal cap that covers anterior two-third of the nucleus.
– Nuclear material (chromatin) gets condensed and the nucleus moves towards one pole of the cell to form the head of the
spermatozoon.
– Centrosome divides into two centrioles. One centriole becomes spherical and gives rise to the axial filament.
– The other centriole moves away from the first centriole and becomes ring shaped. It forms an annulus/ring around the
distal end of the middle piece
