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Developmental Biology. > Oogenesis. > Flashcards

Oogenesis. Flashcards

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1
Q

How are the layers of the egg arranged?

A

Jelly layer.

Outer membrane.

Inner membrane.

Nucleus.

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2
Q

In an egg, what is the outer membrane called?

A

The Vitelline membrane.

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3
Q

What is the Vitelline membrane called in mammals?

A

The zona pellucida.

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4
Q

In an egg, what is the inner membrane called?

A

Cellular plasma membrane.

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5
Q

Is the nucleus in an egg cell, haploid or diploid?

A

Haploid.

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6
Q

What is the germinal vesicle of an egg cell also known as?

A

The nucleus.

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7
Q

What is the purpose of the jelly layer of an egg cell?

A

Protection. Sometimes there are poisons in the jelly layer.

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8
Q

What features can be found in the plasma membrane?

A

Mitochondria and cortical granules.

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9
Q

What is the space between the 2 membranes known as?

A

The perivittelline space.

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10
Q

What can be found in the cytoplasm of the egg?

A

Cellular organelles are in a much higher concentration.

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11
Q

What is the egg yolk used for?

A

Energy.

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12
Q

What is an isolecithal egg?

A

These eggs have a small amount of evenly distributed yolk. The nucleus is centrally located. This occurs in sea urchins and mammals.

These eggs have a very transparent yolk as there is a low concentration.

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13
Q

What is an telolecithal egg?

A

There is a large amount of very dense yolk accumulates at the vegetal end and the nucleus can be found at the animal end. The animal develops on top of the yolk.

This occurs in fish, birds and reptiles.

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14
Q

What is a mesolecithal egg?

A

There is a large amount of dense yolk which accumulates at the vegetal end with less dense yolk at the animal end. The nucleus is found at the opposite end or the animal end.

This occurs in amphibians.

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15
Q

What is a centrolecithal egg?

A

The yolk of this egg is found in the centre and the nucleus is found on the outside of the egg.

This occurs in insects.

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16
Q

When do the PGCs enter meiosis to form oogonium?

A

After they have colonised the gonad and proliferated.

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17
Q

In humans when do the oogonium stop meiotic division?

A

Prophase 1.

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18
Q

Does oogenesis have symmetrical or asymmetrical division?

A

Asymmetrical.

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19
Q

From 1 oogonium what is formed after mitosis?

A

1 egg and 2 polar bodies.

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20
Q

When are the polar bodies lost?

A

After meiosis 1.

After meiosis 2.

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21
Q

The cytoplasm of the ovum contains the materials necessary for what?

A

Early embryonic development.

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22
Q

What are the materials that are found in the cytoplasm?

A

Proteins.

Ribosomes, tRNA and maternal mRNA

Morphogenetic factors.

Protective channels.

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23
Q

What are morphogenetic factors?

A

Morphogenetic factors are proteins and mRNAs that give cells their identity.

They are needed for cell differentiation.

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24
Q

Do amphibians have a self renewing oogonia population or not?

A

They have a self renewing oogonia population.

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25
Q

What is different about the ribosomal gene in frogs?

A

They have multiple copies which can circularise allowing an RNA polymerase to go round and round producing the RNA gene.

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26
Q

What are lampbrush chromosomes?

A

Loops of single stranded DNA.

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27
Q

What is special about lampbrush chromosomes?

A

These allow multiple RNA transcriptions to occur at different chromosomes.

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28
Q

What happens in the previtellogenic phase of a frogs oocycle?

A

RNA’s are put into a dormant form and are activated after fertilisation occurs.

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29
Q

Where does the yolk come from in a frogs egg?

A

It is secreted from the liver of the mother in the form of vitellogenin.

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30
Q

How is the vitellogenin transported from the liver to the egg?

A

In the bloodstream.

31
Q

What is the process by which the egg takes up the vitellogenin?

A

Pinocytosis.

32
Q

How is the 1 large yolk platelet formed?

A

The small vesicles of vitellogenin condense.

33
Q

What is formed during the vitellogenic phase?

A

The yolk of the egg.

34
Q

When can ovulation take place?

A

One year after the vitellogenic phase has ended.

35
Q

What provides the energy for embryonic development?

A

Mitochondria.

36
Q

How is the hypothalamus stimulated in frogs?

A

By an external factor such as spring.

37
Q

Which hormone in frogs stimulates the follicle cells of the ovary and where is it released from?

A

gonadotropin is released from the hypothalamus.

38
Q

What hormone in frogs triggers the oogonia to enter meiosis 1 and where is it released from?

A

Progesterone.

39
Q

Which hormone in frogs de-phosphorylates to activate a maturation promoting factor?

A

C mos.

40
Q

When does ovulation occur in frogs?

A

After meiosis 1.

41
Q

When is the 1st polar body removed from the frogs primary oocyte?

A

After meiosis 1.

42
Q

What protein stops a frogs oocyte developing further than metaphase 2?

A

Cytostatic.

43
Q

What way can the 2ndary oocyte do to develop further than metaphase 2?

A

Undergo fertilisation.

44
Q

Do mammals have self renewing oogonia?

A

No.

45
Q

When is the time that a mammal maximum amount of oogonia present?

A

7th month of foetal development.

46
Q

At what stage do oogonia resume the cell cycle in mammals and when does this occur?

A

The eggs will begin to resume the cell cycle at meiosis 1 once puberty is reached.

47
Q

What signals tell the egg to start the menstrual cycle?

A

GnRH which is a gonadotropin releasing hormone.

FSH which is a follicle stimulating hormone.

48
Q

What does FSH cause the follicles to do?

A

The FSH causes the follicle cells that surround the primary oocyte to start developing and producing oestrogen.

49
Q

What does the oestrogen secreted by the follicles do?

A

Oestrogen inhibits FSH so that only 1 follicle can mature.

50
Q

How does the maturing follicle get FSH if FSH production has been inhibited?

A

It will turn up the FSH expression of cell surface receptors.

Because the remaining follicles don’t have increased receptors for FSH, the remaining FSH will go to the developing follicle cell.

51
Q

How is luteinising hormone produced?

A

The oestrogen also stimulates the hypothalamus which produces GnRH to produce luteinising hormone.

52
Q

What does LH signal for the follicle to do?

A

Luteinising hormone signals for the follicle to erupt and release the oocyte.

53
Q

When does meiosis 1 end with mammalian oogenesis?

A

After the follicle has erupted.

54
Q

What is removed from the oocyte after meiosis 1?

A

A polar body.

55
Q

What triggers the start of meiosis 2?

A

The fertilisation of the oocyte.

56
Q

What is 1st half of the ovarian cycle called?

A

The follicular phase.

57
Q

What is the Graafian follicle?

A

It is the pre-erupted follicle.

58
Q

If 2 follicles are fertilised, what will be the result?

A

Fraternal twins.

59
Q

As the follicle grows, the production of what is significantly increased?

A

Oestrogen.

60
Q

The increased oestrogen production by the follicle results in what?

A

The release of GnRH and causes the release of luteinising hormone in the middle of the cycle.

61
Q

In what stage of oogenesis does the luteal phase take place?

A

The 2nd half. After the follicle has burst.

62
Q

What hormone forms the Graafian follicle?

A

LH.

63
Q

What must occur to the 2ndary oocyte in order for it to progress beyond meiosis 2?

A

Fertilisation.

64
Q

The empty follicle is known as what?

A

The corpus luteum.

65
Q

Which hormones act in sync to support the development of the uterine lining for implantation?

A

Oestrogen and progesterone.

66
Q

The combination of oestrogen and progesterone inhibit the production of what?

A

The production of GnRH and therefore LH and FSH.

67
Q

What happens if fertilisation and implantation do not occur?

A

The decreased amount of FSH will cause the corpus luteum to degenerate.

This will cause a decrease in oestrogen and progesterone resulting in menstruation.

68
Q

What happens if fertilisation and implantation do occur?

A

The corpus luteum will produce relaxin which will soften in order to prepare fibril cartilage in the pelvis for pregnancy.

And Inhibin which inhibits FSH production as we do not want any more ovulations to be stimulated.

69
Q

The 1st stage of the development of the uterine endometrium is stimulated by what?

A

Oestrogen.

70
Q

Insects have what kind of ovary?

A

A telocentric ovary.

71
Q

Describe oogenesis in fruit flies?

A

There is 1 oogonia which undergoes mitotic divisions which produces 16 cells called the cytocytes.

The cell division is incomplete and there are cytoplasmic bridges between the 16 cells, i.e. they share a common cytoplasm.

1 cytocyst will enter meiosis and form a haploid oocyte.

The remaining 15 will remain diploid and become nurse cells.

72
Q

Why do insect oocytes share a common cytoplasm?

A

This allows for the passage of materials between the cells.

73
Q

What do the 15 nurse cells do in an insects oogenesis?

A

They will produce all the material needed for the developing embryo. The cytoplasmic bridges allow for the delivery of these materials to the developing oocyte.

Developmental Biology. (21 decks)

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