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Developmental Biology. > Fertilisation. > Flashcards

Fertilisation. Flashcards

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1
Q

Chemtoctic sperm attraction occurs in what kind of organisms?

A

Marine organisms.

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2
Q

From where on the egg is the chemotactic factor secreted?

A

The eggs jelly coat.

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3
Q

When receptors on the sperm pick up the chemoattractant, what is the reaction of the sperm?

A

The flagella moves faster, this means faster swimming.

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4
Q

When is the acrosomal reaction in the sea urchin triggered?

A

When the sperm makes contact with the jelly layer.

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5
Q

What kind of enzymes from the sea urchin sperm digest the eggs jelly layer?

A

Hydrolytic enzymes.

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6
Q

In which species does the acrosomal reaction take place?

A

All species.

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7
Q

Can the acrosomal reaction be species specific?

A

Yes.

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8
Q

If the acrosomal reaction is species specific, what triggers it?

A

The jelly layer of an egg of the same species.

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9
Q

What ions enter the sperm head once contact with the jelly layer is made?

A

Calcium and sodium ions.

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10
Q

What happens once contact with the sea urchin sperm and the eggs jelly layer is made?

A

Calcium ions are released.

This causes the acrosomal membrane to fuse with the sperm plasma membrane.

The sperm then burrows through the jelly layer.

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11
Q

What protein helps the sperm head to burrow through the jelly layer?

A

Acrosin.

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12
Q

What molecules allow the sperm and the membrane of the zona pellucida to bind?

A

Bindin molecules.

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13
Q

Are bindin molecules very important for species recognition?

A

Yes.

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14
Q

What causes the globular actin in sea urchin sperm to form long filaments?

A

A rise in pH.

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15
Q

What causes extension of the acrosome in sea urchins?

A

The globular actin forming long filaments.

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16
Q

What does the extension of the acrosome help the sea urchin sperm to do?

A

To make contact with the inner membrane. It also exposes the binin molecules.

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17
Q

What effect does the change in pH have on the flagella?

A

It causes it to move much faster.

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18
Q

When the sea urchin sperm reaches the vitelline membrane, what happens?

A

It will nestle between 2 microvilli and the egg will engulf the sperm in a fertilisation cone.

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19
Q

A change in what ratio allows the sperm to fuse to the

A

The cholesterol/phospholipid ratio.

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20
Q

What part of the sperm cell enters the nucleus of the egg?

A

The centriole and the nucleus will enter the egg.

21
Q

What protein drives the acrosomal process in sea urchins?

A

Bindins.

22
Q

What kind of fertilisation occurs in mammals?

A

Internal fertilisation.

23
Q

What has to occur to mammalian sperm to allow it to fertilise an egg?

A

It must be exposed to the fluids of the uterus in the oviduct.

24
Q

What is sperm capacitation?

A

The process by which a change occurs in sperm that allows it to fertilise an egg.

25
Q

What exposes the bindin proteins in mammalian sperm?

A

A protein coating factor is released from the surface of the sperm head. This exposes the bindin proteins that will bind to the eggs zona pellucida.

26
Q

Is sperm egg adhesion species specific in mammals?

A

No.

27
Q

To what protein on the eggs zona pellucida does the sperm bind to in mammals?

A

ZP3 glycoprotein.

28
Q

What molecules of sperm can the ZP3 glycoprotein bind to?

A

Galaxyl-transferase.

SP56.

ZRK.

29
Q

Is there extension of the acrosomal process in mammals?

A

No.

30
Q

What protein drives the acrosomal process in mammals?

A

Fertilin.

31
Q

The fast block changes what about the egg?

A

A change in membrane potential across the eggs plasma membrane.

32
Q

What causes the change in membrane potential?

A

The influx of sodium ions going into the egg.

33
Q

How long does the fast block take to occur?

A

0.1 seconds.

34
Q

How long does the fast block last for?

A

About 1 minute.

35
Q

Does the fast block occur in mammals?

A

No.

36
Q

What is the slow block also known as?

A

The cortical granule reaction.

37
Q

What ions initiate the cortical granule reaction?

A

Calcium ions.

38
Q

What do the cortical granules do to initiate the slow block?

A

They fuse to the eggs plasma membrane and release protease into the perivitteline space which will break the protein bonds.

39
Q

What happens once the protein bonds are broken?

A

Once the bonds have been broken, there will be a separation of the vitelline membrane from the egg plasma membrane.

40
Q

What proteins swell up to increase osmotic pressure in the perivitelline space?

A

Glycosaminoglycans.

41
Q

What protein destroys the eggs bindin receptors?

A

Protease.

42
Q

What proteins are found in the cortical granules that cause the vitelline membrane to harden?

A

Peroxidases.

43
Q

Once the sperm and egg make contact what happens?

A

Fusion of the 2 nucei.

44
Q

Once contact between the egg and sperm occurs, what happens to the sperms DNA?

A

The protamines are removed and they are replaced with histones. T

he chromatin of the sperm is de-condensed and the nuclear membranes fuse, creating a diploid zygote.

45
Q

What is parthogenetic egg activation?

A

This is when the eggs metabolic activation is triggered in the absence of sperm.

46
Q

Once the eggs cytoplasm is rearranged, what is distributed throughout the egg?

A

Morphogens.

47
Q

How does a tunicates cytoplasm rearrange itself after fertilisation?

A

A yellow cytoplasm becomes visible in the vegetal portion of the egg.

Some of the dividing cells will get yellow cytoplasm and some won’t.

The cells that get yellow cytoplasm are directed to become muscle cells.

If the cell gets a grey cytoplasm then it will form mesodermal cells.

48
Q

How does a frogs cytoplasm rearrange itself after fertilisation?

A

In frogs, a pigmented layer of the egg undergoes cortical rotation to reveal, grey cytoplasm that forms opposite the site of sperm entry.

The first cleavage bisects the grey crescent.

The areas of the egg that get the grey cytoplasm will be directed down a certain path.

Developmental Biology. (21 decks)

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