Gametogenesis

Question 1

primordial germ cells (PGC) derived from?

Answer 1

Epiblast and ectoderm

Question 2

What type of cells are primordial germ cells?

Answer 2

Bipotent cells that can form spermatogonia or oogonia.

Question 3

What determines the differentiation of primordial germ cells?

Answer 3

The presence of the SRY gene on the distal end of the short arm of chromosome Y.

Question 4

What happens when the SRY gene is present?

Answer 4

PGC differentiates into spermatogonia.

Question 5

What happens when the SRY gene is absent?

Answer 5

PGC differentiates into oogonia.

Question 6

Where does spermatogenesis occur?

Answer 6

In the seminiferous tubules of the testis.

Question 7

When does spermatogenesis begin?

Answer 7

At puberty.

Question 8

What are the two types of spermatogonia?

Answer 8

Type A: Divides and replenishes spermatogonia.

Type B (pale): Undergoes spermatogenesis.

Question 9

What is the process of sperm release into the lumen of seminiferous tubules called?

Answer 9

Spermiation.

Question 10

How long does spermatogenesis take?

Answer 10

70-74 days (~72 days).

Question 11

How long does spermiogenesis takes place

Answer 11

10-14 days.

Question 12

What is the chromosome number in a primary spermatocyte?

Answer 12

46 (diploid, 2n) XY

Question 13

What happens in meiosis I of spermatogenesis?

Answer 13

Primary spermatocyte (46, 2n) divides into two secondary spermatocytes (23, n).

Question 14

What happens in meiosis II of spermatogenesis?

Answer 14

Secondary spermatocytes (23, n) divide into spermatids (23, n).

Question 15

How many spermatids are formed from one primary spermatogonium?

Answer 15

64 spermatids.

Question 16

What process transforms spermatids into spermatozoa?

Answer 16

Spermiogenesis.

Question 17

stages of Spermatogenesis

Answer 17

Spermatogonia → primary Spermatocyte → Secondary spermatoryte →Spermatids → Sperms

Question 18

1 Spermatogonia gives rise to how many primary Spermatocyte

Answer 18

16

Question 19

each primary Spermatocyte gives rise to how many sperms

Answer 19

4

Question 20

Each Secondary spermatocyte gives rise to how many sperms

Answer 20

2 sperms

Question 21

where does meiosis and mitosis occur in Spermatogenesis

Answer 21

Spermatogonia → mitosis →16 primary spermatocyte → meiosis - I →2 Secondary spermatocyte → meiosis-II → 4 spermatid

Question 23

Each primary spermatogonia gives rise to how many sperms

Answer 23

64 sperms

Question 24

What are the structural analogs between spermatids and sperm?

Answer 24

Nucleus → Head of sperm
Mitochondria → Middle piece (powerhouse of sperm)
Golgi Apparatus → Acrosomal cap
Centriole → Axial filament/tail

Question 25

What is the size of a sperm?

Answer 25

50-60 µm

Question 26

What is the arrangement of the sperm tail?

Answer 26

9+2 microtubule arrangement (formed by the centriole).

Question 27

What is the fertilizable span of sperm?

Answer 27

48-72 hours

Question 28

Where does sperm attain maturity?

Answer 28

Proximal epididymis

Question 29

Where does sperm attain motility?

Answer 29

Distal epididymis

Question 30

How long does it take for sperm to reach the fertilization site after ejaculation?

Answer 30

30 minutes

Question 31

What is the total time taken to form mature sperm (spermatogenesis + maturation)?

Answer 31

90 days

Question 32

How long does epididymal maturation take?

Answer 32

12-14 days

Question 33

What are the key stages of oogenesis?

Answer 33

1. Oogonium undergoes mitosis → Primary oocyte (46, 2n). 2. Meiosis I begins but is arrested in prophase (diplotene stage) → Primary oocyte remains in this stage until puberty. 3. At puberty, LH surge resumes Meiosis I → Formation of secondary oocyte (23, n) and first polar body. 4. Meiosis II begins but is arrested in metaphase. 5. Meiosis II resumes only if fertilization occurs → Formation of ova/female pronucleus (23, n) and second polar body.

Question 34

What is a primordial follicle?

Answer 34

A structure where follicular cells surround the primary oocyte; it is used to assess ovarian reserve.

Question 35

At what stage is the primary oocyte arrested?

Answer 35

Diplotene stage of prophase I (dictate state).

Question 36

When does follicle formation begin?

Answer 36

14 weeks of intrauterine life.

Question 37

When is follicle formation complete?

Answer 37

20-24 weeks of intrauterine life.

Question 38

What is the size of the ovum?

Answer 38

120 µm

Question 39

What is the fertilizable lifespan of an ovum?

Answer 39

12-24 hours

Question 40

What is the size of a follicle just before ovulation?

Answer 40

18-20 mm

Question 41

How many follicles are in the ovary at different stages of life?

Answer 41

| Age | No. of Follicles | |------|----------------| | 5 months of intrauterine life | 6-7 million (max) | | At birth | 1-2 million | | At puberty | 4-5 lakh | | Every month | 1000 follicles undergo atresia | | At menopause | No follicles in ovary |

Question 42

What is the potency of germ cells and zygotes?

Answer 42

Germ cells: Pluripotent (can form all three germ layers). Zygote (after 8-cell stage): Totipotent (can form both embryonic and extraembryonic tissues).

Question 43

What is the migration pathway of germ cells?

Answer 43

Yolk sac → Genital ridge → Gonads form

Question 44

What happens if germ cells fail to migrate?

Answer 44

They end up in an aberrant location and form teratomas.

Question 46

oogonia begins in

Answer 46

intrauterine life

Question 47

What are the compartments of seminiferous tubules?

Answer 47

1. Basal compartment: Contains spermatogonia and primary spermatocytes (early stages of development). 2. Adluminal compartment: Contains secondary spermatocytes, spermatids, and sperm.

Question 48

What is spermiogenesis?

Answer 48

Transformation of spermatids into spermatozoa (sperm)