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BI1051: Genetics and Evolution > Gametogenesis and Fertilisation > Flashcards

Gametogenesis and Fertilisation Flashcards

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1
Q

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

A

Spermatogonia.

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2
Q

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

A

Oogonia.

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3
Q

Define the term primordial germ cell (PGC).

A

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

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4
Q

Where do primordial germ cells originate (PGCs)?

A

In the extra-embryonic tissue.

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5
Q

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

A

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

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6
Q

What does the genital ridge eventually develop into?

A

The somatic cells of the gonad.

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7
Q

What is the importance of meiosis?

A

It introduces genetic variability.

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8
Q

How do PGCs multiply during migration?

A

Via mitosis.

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9
Q

How are spermatocytes produced?

A

Spermatogonia multiply via mitosis to produce spermatocytes.

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10
Q

Spermatocytes enter meiosis. After meiosis what is produced?

A

Haploid spermatids connected by cytoplasmic bridges.

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11
Q

Define synctial cells.

A

Fused cells with multiple nuclei such as spermatids before differentiation.

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12
Q

Why is cytokinesis not completed during Meiosis II?

A

To ensure the haploid spermatids mature in synchrony.

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13
Q

What do spermatids differentiate into?

A

Spermatozoa.

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14
Q

How many spermatozoa are produced from each spermatocyte?

A

Four.

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15
Q

What are the stages of male gametogenesis?

A

PGC, spermatogonia, spermatocytes, spermatids, spermatozoa.

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16
Q

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

A

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

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17
Q

What is contained within the acrosome?

A

Lytic enzymes to digest proteins, lipids and carbohydrates.

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18
Q

What is the axoneme?

A

A cytoskeletal structure that forms the core of the flagellum.

19
Q

How is dynein involved in sperm motility?

A

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

20
Q

When does meiosis occur during spermatogenesis?

A

Before differentiation.

21
Q

When does meiosis occur during oogenesis?

A

After differentiation.

22
Q

How are primary oocytes produced?

A

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

23
Q

When does Meiosis I complete?

A

Upon ovulation.

24
Q

What is produced during Metaphase II?

A

Secondary oocytes.

25
Q

When does Meiosis II complete?

A

After fertilisation.

26
Q

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

A

1 ova and 2 polar bodies.

27
Q

What surrounds a mammalian oocyte?

A

The zona pellucida.

28
Q

What is the zona pellucida?

A

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

29
Q

What is the significance of the ZP3 glycoprotein?

A

It is the sperm receptor and ensures species specificity.

30
Q

What are cortical granules?

A

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

31
Q

Why are cortical granules important?

A

They prevent polyspermy (multiple fertilisations).

32
Q

What is the first stage of fertilisation?

A

Sperm binding to zona pellucida.

33
Q

What is the second stage of fertilisation?

A

The acrosome reaction.

34
Q

What is the third stage of fertilisation?

A

Penetrating the zona pellucida.

35
Q

What is the fourth stage of fertilisation?

A

The fusing of membranes.

36
Q

What is the fifth stage of fertilisation?

A

Sperm nucleus and contents enter the cell cytoplasm.

37
Q

What surrounds the zona pellucida?

A

Cumulus cells.

38
Q

Name the recognition protein for ZP3.

A

Sperm galactotransferase (GalT).

39
Q

What does GalT clustering trigger during fertilisation?

A

G protein activation and a change in membrane potential.

40
Q

What is the acrosomal reaction?

A

Calcium-mediated exocytosis of the

acrosomal vesicle being initiated.

41
Q

What 3 processes occur in the oocyte after fertilisationi?

A
  1. Exocytosis of cortical granules.
  2. Completion of Meiosis II.
  3. Metabolic activation.
42
Q

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

A

Calcium ions from the endoplasmic reticulum.

43
Q

What does the sperm provide?

A

A haploid genome and a centriole.

44
Q

What does the ovum provide?

A

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

BI1051: Genetics and Evolution (13 decks)

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