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Developmental biology > Lecture 1 - Gametes&Fertilazation > Flashcards

Lecture 1 - Gametes&Fertilazation Flashcards

1
Q

What is meiosis?

A

Gametes get half the number of chromosomes

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2
Q

Can you explain the steps during meiosis to produce haploid daughter cells? (Telophase)

A

1) The DNA condenses to become the sister chromatids
2) Metaphase 1 - Sister chromatids move to the centre of the cell by spindle fibres formed by the centrioles. Crossing over genetic information happens.
3) Anaphase 1 - The Sister Chromatids, split into 2 diploid chromosomes because the spindle fibres contract towards the centrioles.
4) Metaphase 2 / anaphase 2- Same as metaphase however, the diploid chromosomes become haploid
5) Produces for gametes

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3
Q

When and where does spermatogenesis begin?

A

In puberty in the testis

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4
Q

What are spindle fibres made of?

A

Protein structures.

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5
Q

Can you recall the tissues that Spermatogenesis uses to produce spermatozoa? (5 tissues)

A

1) Spermatogonia are diploid cells and are progenitor cells for spermatogenesis.
2) Spermatocyte 1 - initiates meiosis, however still diploid cells.
3) Spermatocyte 2 - The cells that go through meiosis and are haploid cells, change shape to form Spermatid
4) Spermatid- finished product of spermatocyte 2, immature spermatozoa
5) Spermatozoa - Released in the lumen as a mature male sex cell.

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6
Q

Can you explain the structure of spermatozoa?

A

Head - Ancrosomes /Nucleus/ Centriole
Tail - Mitochondria / Tail

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7
Q

What are the three phases in spermatogenesis called?

A

1) Proliferative phase - Retinoic Acid at puberty induces Spermatogonia to increase by mitosis

2) Meiotic Phase - Produces haploid spermatids

3) Post-meiotic shaping - Post-meiotic shaping called spermiogenesis produces spermatozoa

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8
Q

Where does spermatogenesis take place?

A

Seminiferous tube

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9
Q

Can you explain how Seprmiogenesis shapes a spermatocyte into spermatozoa?

A

1) The Golgi apparatus first forms the acrosomal vesicle and granule and then detaches.
2) Centriol attaches to the nucleus and starts forming the flagellum made of tubulin protein
3) The acrosomal vesicle moves towards the wall of the cell, and the flagellum grows larger forming spermatozoa.

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10
Q

Why is the Golgi apparatus important in Spermiogenesis?

A

Produces the acrosomal vesicle and granules on spermatozoa

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11
Q

Where are spermatozoa collected after they released from the testis?

A

Epididymis

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12
Q

Can you define Capacitation?

A

The final maturation of sperm in the female reproductive tract

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13
Q

Can you define Oogenesis?

A

The formation of the egg

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14
Q

What does Luteneizing hormone due in Oogenesis

A

Hormone induces the eggs of a female to progress in meiosis

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15
Q

What is an important peculiarity in Oogenesis Meiosis?

A

1) Only gamete is pronounced an can fertilise, the rest of the cells become polar bodies
2) Fertilisation takes place during second metaphase (In humans)

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16
Q

Explain the structure of the Ooctye

A

1) Cumulus - nearer the egg is called the Corona Radiata
2) Matrix - Zona pellucida proteins
3) Membrane
4) Nucleus of egg

17
Q

What is find in the Nucleus of the egg?

A

1) Mitochondria
2) Nutritive proteins (Yolk Proteins) - produced in liver
3) Ribosomes and tRNA
4) mRNA
5) Morphogenic factors controlling expression

18
Q

Where is the egg released and fertilisation take place?

A

Ampulla

19
Q

Why is the Comulus important in the Ampulla?

A

For the translocation of the egg

20
Q

How does sperm travel to the egg?

A

1) Sperm swims towards the cervical mucus
2) It is then transported by uterine muscle contraction

21
Q

What is Sperm rheotaxis?

A

Sperm swim towards the flow of liquid in the oviduct

22
Q

Why is fertilisation really difficult?

A

Sperm moving to quickly into the ampulla do not capacitate
Sperm are capacitated for a short period of time in the ampulla

23
Q

What is done by the female to increase the chances of fertilisation and block polyspermy?

A

Sperm is released in packets of capacitated sperm to extend fertilisation window

24
Q

What is capacitation?

A

The molecular process of capacitation prepare the sperm to the acrosome reaction & enable the sperm to became Hyperactive

25
Q

How does capacitation accur?

A

Lipid changes
1) Cholesterol is removed by Albumin in the female
2) Receptors bind the egg Zona Pellucida are exposed
3) Acrosome reaction

26
Q

Why does Cholesterol removal cause a dramatic change in the sperm membrane?

A

Signal induces a cascade of modification of many important proteins in the cytoplasm

27
Q

Where is Sperm temporary stored before it is capacitated?

A

Uncapacitated Sperm temporarily bind to Isthmus

28
Q

What does hyper activation of sperm mean?

A

Capacitated sperm swim with more force and rotate on its axis - this occurs by ion channels opening in membrane of the sperm tails

29
Q

What is sperm thermotaxis?

A

Sperm swim towards higher temperature: 2C gradient between isthmus and ampulla

30
Q

What is sperm chemotaxis?

A

Oocyte and Cumulus released molecule to attract sperm

31
Q

Explain the Acrosomal reaction

A

1) Sperm binds to zona pellucida
2) Acrosome reaction
3) Sperm lyses hole in Zona
4) Sperm and egg membrane fuse

32
Q

Which proteins does sperm bind in the Zona Pellucida?

A

ZP2-3 proteins of the Zona Pellucida

33
Q

Why is Izumu important after achrosomal reaction?

A

Izumu binds to proteins Juno and CD9 which are expressed on the membrane of the egg fusing the sperm and egg membrane

34
Q

How does the female egg gamete block polyspermy?

A

1) Immediately after fusion a layer of cytoplasm release cortical granule
2)enzyme digesting the zona pellucita
3) Zona pellucita matrix ditaches the ZP2 proteins.

35
Q

Could you recall Genetic Fusion?

A

1) Male pronucleous produce aster
2) Female oocyte complete second meiotic division
3) Male centriole organises the Zygotic spindle
4) Male and female organised together by spindle

36
Q
A

Developmental biology (1 decks)

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