Topic 2: Gametogenesis

Question 1

Phases of Gametogenesis

Answer 1

1. Generation of germ cells and migration to the gonads
2. Multiplication of germ cells in the gonads (mitosis)
3. Reduction in chromosome number by half (meiosis)
4. Maturation and differentiation

Question 2

• Arise outside the gonad:
• Recoanizable at early stage of development

Answer 2

Phase 1:
Generation of germ cell and migration to the gonads

Question 3

cells are identified in the yolk sac endoderm

are large sized, high content of alkaline phosphatase

Answer 3

PGCs

Question 4

PGCs in ___ recognizable at 24-day post fertilization in the yolk sac endoderm

Answer 4

humans

Question 5

who concluded that In the mouse:
PGCs originally reside in the epiblast of gastrula

Answer 5

Hannel & Eddy (1986)

Question 6

who localized the region in the Extra Embryonic mesoderm posterior to the primitive streak in a 7.25t day embryo

Answer 6

Ginsburg (1990)

Question 7

In humans:
By 3rd week, the PCs wander in what manner:

Answer 7

amoeboid manner

Question 8

journey of human PCs By 3rd week

Answer 8

Primary ectoderm → Yolk sac wall → Near exit of allantois

Question 9

In humans

PC generation

Answer 9

3-week old embryo showing the PCs in the wall of the yolk sac close to the attachment of the allantois

Migration pathway of the PCs along the wall of the hindgut and the dorsal mesentery → genital ridge

PGCs are now extra embryonal in the yolk sac wall

PCs migrate from extraembryonic mesoderm of allantois → embryo proper

Question 10

In Rodents (as mammalian model)
development of PGCs depend on signals
radical expression of pluripotency markers, such as

Answer 10

Oct-4+, NANOG, and SOX2 genes

Question 10

In Rodents (as mammalian model)
development of PGCs depend on signals
radical expression of pluripotency markers, such as

Studies strongly suggests:

Answer 10

BMP (bone morphogenetic protein) signal factor

Question 10

Proposed migration pathway

Answer 10

Primary ectoderm

Yolk sac endoderm
PGCs become extraembryonal

Allantois
PGCs become specified at the base

Dorsal mesentery

Left & Right genital ridges
In the embryo proper

Question 11

The life cycle of murine germ cells

After fertilization:

Answer 11

Zygote → cleaving forming a 2-cell embryo → giving rise to the blastocyst
Blastocyst consists of the trophectoderm , and the inner cell mass

Question 11

The life cycle of murine germ cells

At gastrulation:

Answer 11

A new germ layer → the mesoderm (blue)
The primordial germ cells are specified at E7.25 at the base of the mesodermal allantois

Question 11

The life cycle of murine germ cells

After implantation

Answer 11

Inner cell mass/epiblast (orange) → cavitation and epithelializes

Question 11

Upon sex determination: female (oogonia) and male(spermatogonia) germ cells follow different fates

describe those fates

Answer 11

In the ovary (top row), the oocytes mature in their follicles → released during ovulation.

In the testis (bottom row), spermatogenesis takes place to generate motile sperm cells

Question 11

PGCs migrate through the

Answer 11

forming hindgut → dorsal mesenterium → genital ridges

Question 12

Proliferation of germ cells (mitosis)

Mitotic patterns in the gonads differ widely between males and females

Answer 12

AI Overview
Mitotic patterns differ in male and female gonads primarily due to sex-specific developmental timing, with female germ cells entering meiosis earlier in fetal development, while male germ cells do so post-puberty. Female development involves long-term meiotic arrest in the embryo, whereas male development involves prolonged mitotic proliferation to build up a large population of sperm precursors. T

Question 13

Oogenesis in Amphibian

Egg maturation requires

Answer 13

3 years

Question 13

Distinct features of oogenesis

Answer 13

Oocytes undergo arrested stages
Unequal cytoplasmic division
Only one functional oocyte produced per cycle; polar bodies produced

Question 13

Oogenesis in Amphibian

Mitosis is

Answer 13

continuous

Question 13

In most animals, growing oocytes are actively

Gene products (cell metabolism, oocyte-specific processes, early development prior to nuclear function)

Answer 13

transcribing genes

Question 14

Spermatogenesis

Mitosis in male occurs

Answer 14

throughout life

Question 15

Spermatogenesis pathway

Answer 15

PGCs at the genital ridge → sex cords → seminiferous tubules → tubular epithelial sertoli cells

Question 16

Categories of changes during spermiogenesis

Answer 16

A) Reorganization of the cytoplasm B) Progressive reduction in nuclear size/compaction of the nucleus

Question 17

Categories of changes during spermiogenesis A) Reorganization of the cytoplasm what organelles are involved?

Answer 17

Golgi apparatus Centrioles Mitochondria

Question 18

Categories of changes during spermiogenesis B) Progressive reduction in nuclear size/compaction of the nucleus what processes are involved?

Answer 18

Nuclear elongation Loss of water Centrioles Elimination of RNA; leaving only DNA