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BB20149 > Gametogenesis > Flashcards

Gametogenesis Flashcards

1
Q

What is the default sex in gametogenesis?

A

Female.

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2
Q

What is the Sry?

A

The test-determining factor.

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3
Q

What happens if Sry is absent?

A

The sex is female.

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4
Q

What does the Sry activate?

A

Sox9.

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5
Q

What is the result of Sry being present?

A

It induces sex cords that form seminiferous tubules.

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6
Q

What do seminiferous tubules contain?

A

Sertoli cells and leydig cells.

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7
Q

What are sertoli cells?

A

They are cells that secrete anti-Mullerian hormone to prevent female development.

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8
Q

What are leydig cells?

A

Cells that secrete testosterone to promote development of the male reproductive system.

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9
Q

What is spermatogenesis?

A

The process from which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testes.

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10
Q

When does spermatogenesis initiate?

A

Puberty.

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11
Q

When does differentiation of spermatozoa occur?

A

When the threshold of BMP8b is reached.

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12
Q

What else happens in mammalian spermatogenesis?

A

There is anchoring to sertoli cells via N-cadherin.

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13
Q

What is the first committed stem cell type in mammalian spermatogenesis?

A

The intermediate spermatogonia.

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14
Q

What is the last mitotic division in mammalian spermatogenesis?

A

The change from type B spermatogonia to primary spermatocytes.

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15
Q

What is differentiation favoured by?

A

Low concentration GDNF and high concentration SCF.

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16
Q

What produces GDNF and SCF?

A

Sertoli cells.

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17
Q

What happens in meiosis?

A

Secondary spermatocytes form from primary spermatocytes.

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18
Q

What happens in spermiogenesis?

A

Residual bodies are formed from spermatids.

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19
Q

What is spermiogenesis?

A

Post-meiotic generation of sperm.

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20
Q

What happens in post-meiotic generation of sperm?

A

A round spermatid develops to a testicular sperm.

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21
Q

What is the starting point of mammalian spermiogenesis?

A

It begins with a non-flaggelar haploid round spermatid.

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22
Q

What happens with the golgi apparatus in spermiogenesis?

A

It forms the acrosome which covers part of the nucleus. On the basement side, the flagella sticks into the lumen.

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23
Q

What are histones replaced in during spermiogenesis?

A

Protamine.

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24
Q

What happens when histones are replaced with protamine?

A

There is non-nucleosomal chromatin and transcription almost completely shuts down.

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25
Q

What is the structure of chromatin at the start of spermiogenesis?

A

It is nucleosomal.

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26
Q

What are histones replaced with in spermatids in sperm chromatin formation?

A

Transition proteins - tnp1 and tnp2 in round spermatids.

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27
Q

What is established in spermiogenesis?

A

Paternal imprints.

28
Q

What does spermiogenesis result in?

A

Non-nucleosomal chromatin.

29
Q

What happens to transcription during spermiogenesis?

A

It almost completely shuts down.

30
Q

What is significant about chromatin at the beginning of spermiogenesis?

A

It is nucleosomal.

31
Q

What are histones replaced by in spermiogenesis?

A

Transition proteins TNp1 and Tnp2 in round spermatids.

32
Q

What is the distinction between round spermatids and elongating spermatids?

A

Round spermatids contain transition proteins that have replaced histones, whereas elongating spermatids

33
Q

How long does spermatogenesis take in humans?

A

65 days.

34
Q

What happens to cells, in terms of distance from the basal lamina, during differentiation?

A

They move further away.

35
Q

What transcription factor is essential for spermatogenesis?

A

TAF4b testis-specific TBP associated transcription factor.

36
Q

What is the epididymis?

A

A duct behind the testis where sperm passes to the vas deferens.

37
Q

What needs to happen to testicular sperm?

A

As testicular sperm are not capable of fertilisation (and lack forward motility), this ability needs to be acquired during epidymidal transit.

38
Q

What happens during epididymidal transit?

A

They undergo extensive membrane changes.

39
Q

What is oogenesis?

A

Differentiation of the female gamete, the oocyte.

40
Q

What are the two types of oogenesis?

A

Continuous and finite oogenesis.

41
Q

What is continuous oogenesis?

A

Ooogenesis from self-sustaining population of mitotically dividing oogonia. It is similar to spermatogonia and occurs in fish, amphibia, sea urchins and insects.

42
Q

What is finite oogenesis?

A

When it is generated in the embryo and arrested until small numbers resume meiosis. This occurs in birds, mammals and reptiles - only a few eggs are generated until they are released or fertilised.

43
Q

Where does oogenesis occur in mammals?

A

It occurs in the ovaries and is associated with granulosa cells that become cumulus cells.

44
Q

What are granulosa cells?

A

A somatic cell of the sex cord closely associated with the developing female gamete.

45
Q

What is the purpose of granulosa cells?

A

They provide nutrition and support maturation.

46
Q

What are some of the hormones that are involved in oogenesis?

A

Follicle stimulating hormone and luteinizing hormone.

47
Q

What produces follicle stimulating hormone (FSH)?

A

The anterior pituatory gland.

48
Q

What is the purpose of follicle stimulating hormone?

A

It stimulates the growth of ovarian follicles.

49
Q

What is ovulation stimulated by?

A

A surge in leteinizing hormone.

50
Q

What is luteinizing hormone produced by?

A

The anterior pituatory gland.

51
Q

What is the structure of FSH?

A

It is an alpha/beta subunit heterodimer.

52
Q

What is the structure of leutinizing hormone?

A

It is an alpha/beta heterodimer. The alpha subunit is shared with FSH.

53
Q

What is the zona pellucida?

A

A unique glycoprotein matrix surround the oocyte.

54
Q

What happens if the zona pellucida is removed?

A

Infertility.

55
Q

What proteins is the zona pellucida made up of in humans and mice?

A

3 proteins in mice and 4 in human - ZP1, ZP2, ZP3, (ZP4).

56
Q

What are the glycoproteins linked to in the zona pellucida?

A

O and N.

57
Q

When are the zona pellucida proteins synthesised?

A

Oocyte growth phase.

58
Q

What is significant about the ZP2 in the zona pellucida?

A

It is a receptor for sperm binding.

59
Q

When is meiosis resumed in the oocyte?

A

It resumes from prophase 1 (check this ?) arrest after follicle growth, which is stimulated by FSH.

60
Q

What is GVBD?

A

Germinal vesicle breakdown.

61
Q

When does GVBD occur?

A

The end of prophase 1 - diplotene.

62
Q

What is the polar body a product of?

A

Asymmetric cytokinesis.

63
Q

When were mouse spermatids produced in vitro?

A

March 2016. They started from embryonic stem cells.

64
Q

What can spermatids produced in vitro be used for?

A

Injection into a naturally produced mii oocytes - 1.9-2.7% 2-cell embryos develop to healthy offspring.

65
Q

When were oocytes produced in vitro?

A

October 2016.

66
Q

How were oocytes produced in vitro?

A

iPS cells or ES cells.

BB20149 (16 decks)

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