Gametogenesis and Fertilisation

Question 1

What term is given to germ cells that move into the testes?

Answer 1

Spermatogonia.

Question 2

What term is given to germ cells that move into the ovaries?

Answer 2

Oogonia.

Question 3

Define the term primordial germ cell (PGC).

Answer 3

The precursors to gametes which later develop, via meiosis, into sperm or egg cells.

Question 4

Where do primordial germ cells originate (PGCs)?

Answer 4

In the extra-embryonic tissue.

Question 5

Where do PGCs migrate (in terms of inside the embryo) and what route do they take?

Answer 5

They migrate into the embryo via the gut and into the genital ridge.

Question 6

What does the genital ridge eventually develop into?

Answer 6

The somatic cells of the gonad.

Question 7

What is the importance of meiosis?

Answer 7

It introduces genetic variability.

Question 8

How do PGCs multiply during migration?

Answer 8

Via mitosis.

Question 9

How are spermatocytes produced?

Answer 9

Spermatogonia multiply via mitosis to produce spermatocytes.

Question 10

Spermatocytes enter meiosis. After meiosis what is produced?

Answer 10

Haploid spermatids connected by cytoplasmic bridges.

Question 11

Define synctial cells.

Answer 11

Fused cells with multiple nuclei such as spermatids before differentiation.

Question 12

Why is cytokinesis not completed during Meiosis II?

Answer 12

To ensure the haploid spermatids mature in synchrony.

Question 13

What do spermatids differentiate into?

Answer 13

Spermatozoa.

Question 14

How many spermatozoa are produced from each spermatocyte?

Answer 14

Four.

Question 15

What are the stages of male gametogenesis?

Answer 15

PGC, spermatogonia, spermatocytes, spermatids, spermatozoa.

Question 16

What changes occur during spermiogenesis (spermatids differentiating into spermatozoa)?

Answer 16

Golgi develops into acrosomal cap.
Flagellum develops.
Mitochondria coalesce at flagellum.
Cytoplasmic bridges are lost.

Question 17

What is contained within the acrosome?

Answer 17

Lytic enzymes to digest proteins, lipids and carbohydrates.

Question 18

What is the axoneme?

Answer 18

A cytoskeletal structure that forms the core of the flagellum.

Question 19

How is dynein involved in sperm motility?

Answer 19

It is a motor protein that uses energy from ATP hydrolysis to move microtubules past one another.

Question 20

When does meiosis occur during spermatogenesis?

Answer 20

Before differentiation.

Question 21

When does meiosis occur during oogenesis?

Answer 21

After differentiation.

Question 22

How are primary oocytes produced?

Answer 22

Oogonia enter meiosis and arrest in Prophase I to form primary oocytes.

Question 23

When does Meiosis I complete?

Answer 23

Upon ovulation.

Question 24

What is produced during Metaphase II?

Answer 24

Secondary oocytes.

Question 25

When does Meiosis II complete?

Answer 25

After fertilisation.

Question 26

How many ova and polar bodies are produced from each primary oocyte?

Answer 26

1 ova and 2 polar bodies.

Question 27

What surrounds a mammalian oocyte?

Answer 27

The zona pellucida.

Question 28

What is the zona pellucida?

Answer 28

A translucent layer of 3 glycoproteins: ZP1, ZP2 and ZP3.

Question 29

What is the significance of the ZP3 glycoprotein?

Answer 29

It is the sperm receptor and ensures species specificity.

Question 30

What are cortical granules?

Answer 30

Organelles derived from the golgi apparatus. They contain proteases and glycosidases.

Question 31

Why are cortical granules important?

Answer 31

They prevent polyspermy (multiple fertilisations).

Question 32

What is the first stage of fertilisation?

Answer 32

Sperm binding to zona pellucida.

Question 33

What is the second stage of fertilisation?

Answer 33

The acrosome reaction.

Question 34

What is the third stage of fertilisation?

Answer 34

Penetrating the zona pellucida.

Question 35

What is the fourth stage of fertilisation?

Answer 35

The fusing of membranes.

Question 36

What is the fifth stage of fertilisation?

Answer 36

Sperm nucleus and contents enter the cell cytoplasm.

Question 37

What surrounds the zona pellucida?

Answer 37

Cumulus cells.

Question 38

Name the recognition protein for ZP3.

Answer 38

Sperm galactotransferase (GalT).

Question 39

What does GalT clustering trigger during fertilisation?

Answer 39

G protein activation and a change in membrane potential.

Question 40

What is the acrosomal reaction?

Answer 40

Calcium-mediated exocytosis of the | acrosomal vesicle being initiated.

Question 41

What 3 processes occur in the oocyte after fertilisationi?

Answer 41

1. Exocytosis of cortical granules. 2. Completion of Meiosis II. 3. Metabolic activation.

Question 42

What does sperm entry trigger the release of? What organelle is the source of this?

Answer 42

Calcium ions from the endoplasmic reticulum.

Question 43

What does the sperm provide?

Answer 43

A haploid genome and a centriole.

Question 44

What does the ovum provide?

Answer 44

A haploid genome, mitochondria (and other organelles) and mRNAs/proteins for early development.