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BB20149 > Gametogenesis 1 > Flashcards

Gametogenesis 1 Flashcards

1
Q

What is gametogenesis?

A

The process by which gametes (sperm and egg cells) are formed.

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2
Q

What does it mean that gametogenesis is compartmentalized in mammals?

A

It occurs separately from the development of somatic tissue.

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3
Q

What does gametogenesis include in animals?

A

Meiosis which is a unique cell cycle where there is recombination between homologous chromosomes to produce haploid cells.

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4
Q

What are primordial germ cells?

A

These are cells that are specified as germline cells, including in the gonads and in regions where they are specified before gonads.

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5
Q

What is the germ plasm?

A

A specialised cytoplasm in egg cells (not mammals) that predetermines germ cells. It is localised to one part of the egg.

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6
Q

What are examples of species that have a germ plasm?

A

Nematodes, insects and amphibians.

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7
Q

Where do primordial germ cells form?

A

In the posterior proximal epiblast.

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8
Q

What happens is primordial germ cells are cultured in vitro?

A

They form embryonic germ cells.

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9
Q

What does it mean that embryonic germ cells are pluripotent?

A

They can give rise to all cells of an adult, but not form an entire human.

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10
Q

What are PGCs called when they arrive at the genital ridge?

A

Gonocytes.

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11
Q

What happens when PGCs arrive at the gonad, in terms of division?

A

They divide mitotically.

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12
Q

How are parental genomes marked differently?

A

They are imprinted.

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13
Q

What are the phases of prophase in meiosis 1?

A

Leptotene, zygotene, pachytene, diplotene, diakinesis

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14
Q

What happens in the first phase of prophase in meiosis 1?

A

(Leptotene) - DNA replication is finished, sister chromatids are thin and closely associated and chromosomes begin condensing.

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15
Q

What happens in the second phase of prophase in meiosis 1?

A

(Zygotene) - There is bivalent formation and cohesin rings encircle sister chromatids. It requires a synaptonemal complex

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16
Q

What happens in the third phase of prophase in meiosis 1?

A

(Pachytene) - condensation continues, the synaptonemal complex breaks down, crossing over occurs.

17
Q

What happens in the fourth phase of prophase in meiosis 1?

A

(Diplotene) - chiasmata are visible at the cross-over points, the synaptonemal complex breakdown is complete, homologous chromosomes separate and transcription occurs.

18
Q

What happens in the fifth phase of prophase in meiosis 1?

A

Kinetochores move away from each other and the chromosomes remain joined at the tips.

19
Q

What happens in metaphase 1?

A

There is nuclear membrane breakdown, the chromosomes assemble on the metaphase plate, spindle assembly checkpoint - the chromosomes must be properly aligned on spindles.

20
Q

What does cyclin B do in metaphase 1?

A

It prevents degradation until the spindle assembly checkpoint is complete.

21
Q

What is aneuploidy?

A

Having an abnormal number of chromosomes.

22
Q

What happens in anaphase 1?

A

Homologous chromosomes separate.

23
Q

What happens in telophase 1?

A

Two cytokinetic products form - each has a full set of homologous partners.

24
Q

What is the other name for interkinesis and what is it?

A

Interphase II - it is a period of rest that some species have between meiosis I and II.

25
Q

What is the difference between meiosis in males and females?

A

In males there is completion of meiosis II, but metaphase II is arrested in females until fertilisation.

26
Q

What is non-dysjunction and when does it occur?

A

The failure of sister chromatids to separate properly during cell divison. It happens during anaphase I or II.

27
Q

What are some of the conditions that arise as a result of non-dysjunction?

A

Down syndrome, Turner’s syndrome.

28
Q

What is Turner’s syndrome?

A

Only one x chromosome is present - it is only a condition present in females. It is a neurological condition that can result in weight issues, heart problems and ovarian problems.

29
Q

What is Klinefelter’s syndrome?

A

An extra X chromosome in men - can result in abnormal height, delayed puberty and sex organ defects.

BB20149 (16 decks)

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