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Developmental Biology. > PGC's and Spermatogenesis. > Flashcards

PGC's and Spermatogenesis. Flashcards

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1
Q

What are primordial germ cells?

A

They are large spheric diploid cells that are formed in the early stages of embryonic development and are precursors of the oogonia and spermatogonia.

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2
Q

Where are primordial germ cells formed?

A

They are formed outside the gonads and migrate to the embryonic ovaries and testes for maturation.

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3
Q

What determines the primordial germ cells?

A

mRNA containing germplasm determines the primordial cells.

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4
Q

What is the bottom half of the egg called?

A

The vegetal pole.

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5
Q

What is the top half of the egg called?

A

The animal pole.

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6
Q

What is the blastocoel?

A

The blastocoel is fluid filled spaced that forms within the fertilised egg on the 5th day after conception.

It stores all the nutrients for the developing embryo.

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7
Q

What determines PGCs in amphibians?

A

Germ plasm.

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8
Q

How do the PGC’s move to the gonadal ridges in amphibians?

A

The germ plasm begins to migrate along a cleavage furrow that appears at the animal pole (top half of the egg). The germ plasm then segregates into cells lining the floor of the blastocoele.

Blastomeres containing germ plasm differentiate into primordial germ cells. The PGCs migrate into the gonadal ridges.

Once inside the gonads the PGCs then proliferate and become either sperm cells or egg cells.

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9
Q

What is the germ plasm in an amphibian egg?

A

The germ plasm, is an RNA rich cytoplasm at the eggs vegetal pole.

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10
Q

How do the PGC’s move to the gonadal ridges in mammals?

A

They migrate up the hind-gut and dorsal mesentery.

They then proliferate and enter the gonadal ridges.

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11
Q

How do PGC’s move?

A

Via extension of the filopodia.

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12
Q

How do the PGC’s move to the gonadal ridges in birds and reptiles?

A

The primordial germ cells originate in the epiblast and then migrate to a region called the germinal crescent which is at the anterior border of the area zona pellucida.

They then proliferate.

The PGC’s then squeeze through the walls of developing blood cells and enter the blood stream.

They migrate through the bloodstream to the gonad primordial and then exit the blood vessels and enter the gonadal ridges.

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13
Q

What is the process by which PGC’s move into the bloodstream and to the gonadal ridges?

A

Diapedesis.

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14
Q

What is germ plasm?

A

Germ plasm is an RNA rich cytoplasm.

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15
Q

What are the mechanisms that allow PGCs to find the gonad in zebra fish?

A

In zebra fish, there is a molecule called chemokine stromal cell factor 1 which is excreted from the gonads.

The PGC’s move up the concentration gradient.

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16
Q

What is chemotaxis?

A

This is when a cell can sense a molecule through cell surface receptors and it moves from an area of low concentration of that molecule to an area of high concentration.

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17
Q

What happens chemokine stromal cell factor 1 is disrupted?

A

The germ cells do not know where to go.

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18
Q

What is the name of chemotaxis that occurs in mice?

A

Stem cell factor.

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19
Q

What is contact guidance?

A

There is also contact guidance where certain molecules called fibronectin on the surface of cells will provide a map or road to the gonad region.

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20
Q

Which has more cytoplasm, a sperm cell or an ovum cell?

A

Ovum.

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21
Q

Do sperm cells undergo symmetric or asymmetric meiosis?

A

Symmetric.

22
Q

Do ovum cells undergo symmetric or asymmetric meiosis?

A

Asymmetric.

23
Q

How many sperm cells are produced via meiosis of 1 PGC?

A

4.

24
Q

How many ovum are produced via meiosis of 1 PGC?

A

1 and 2 polar bodies.

25
Q

Which is more variable, oogenesis or spermatogenesis?

A

Oogenesis.

26
Q

What is a steel mutation?

A

There is a recessive gene that stops stem cell factor which signals for PGCs to start dividing on their way to the gonad. This means there are not enough PGCs when they reach the gonad resulting in a sterile mice.

27
Q

What is a white spotting mutation?

A

This is when the gene that produces the cell surface receptor or the signal molecule involved in stem cell factor is defective and this results in a sterile mouse.

28
Q

List the order which different spermatogonia are formed?

A

Type A1 spermatogonia.

Type A2 spermatogonia.

Type A3 spermatogonia.

Type A4 spermatogonia.

Intermediate spermatogonia.

Type B spermatogonia.

Primary spermatocyte.

Secondary spermatocyte.

Spermatids.

29
Q

Type A1 spermatogonia can make what sperm cells?

A

More type A1s or type A2s.

30
Q

Type A2 spermatogonia can make what sperm cells?

A

More type A2s or type A3s.

31
Q

Type A3 spermatogonia can make what sperm cells?

A

More type A2s or type A3s.

32
Q

Type A4 spermatogonia can make what sperm cells?

A

More type A4s or intermediate spermatogonia.

33
Q

Intermediate spermatogonia can make what sperm cells?

A

More intermediate spermatogonia or type B.

34
Q

Primary spermatocytes can make what sperm cells?

A

Secondary spermatocytes.

35
Q

Secondary spermatocytes can make what sperm cells?

A

Spermatids.

36
Q

Why are so many different sperm cells produced?

A

So there can be a huge wave of production.

37
Q

Which types of sperm cells are diploid?

A

Type A1 spermatogonia.

Type A2 spermatogonia.

Type A3 spermatogonia.

Type A4 spermatogonia.

Intermediate spermatogonia.

Type B spermatogonia.

Primary spermatocytes.

38
Q

What kind of sperm cells are haploid?

A

Secondary spermatocytes.

Spermatids.

39
Q

At what stage do spermatids get their flagella?

A

At the end of meiosis 2.

40
Q

What fuses to form the spermatids acrosome?

A

Golgi vessels.

41
Q

Where is the acrosome located in the spermatid?

A

At the tip of its head.

42
Q

What does the acrosome contain?

A

Protease enzymes.

43
Q

What is the flagella made up of?

A

Centrioles.

44
Q

What cell organelle is found in abundance around the flagella?

A

Mitochondria.

45
Q

When is the spermatids cytoplasm removed?

A

When the DNA is condensed into the sperm head.

46
Q

What is a synctium?

A

These are cytoplasmic bridges that link cells together in spermatogenesis and allows synchronised development, division and differentiation.

47
Q

What is the name of the structure which DNA wraps around in the spermatid?

A

Protamines.

48
Q

Why does the DNA wrap around proteomes in spermatids, rather than histones?

A

Histones are too large to fit in the sperm cell.

49
Q

When do PGCs become visible in mammals?

A

In mammals PGCs become conspicuous when they are 10-100 large, alkaline phosphatase rich cells in the region of the extra embryonic yolk.

50
Q

Type B spermatogonia can make what sperm?

A

They are the last cells to undergo mitosis to form primary spermatocytes.

Developmental Biology. (21 decks)

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