Fertilisation and Embryo Cleavage Flashcards Preview

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Flashcards in Fertilisation and Embryo Cleavage Deck (33)
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1

What percentage of oocytes is chromosomally abnormal?

20-37%

2

What percentage of sperm is chromosomally abnormal?

7-15%

3

What percentage of zygotes is chromosomally abnormal and undergoes spontaneous abortion?

40%

4

How long may sperm wait in the female reproductive tract?

5-6 days.

5

At what points does meiosis pause in females?

At prophase I in embryogenesis, at metaphase II during puberty

6

What happens during synapsis?

Crossing over

7

What is a chiasma in terms of meiosis?

Areas where homologous chromosomes are locked together during recombination.

8

How many diploid combinations are possible?

64 trillion

9

What is turner syndrome?

X

10

What is Kleinfelter syndrome?

XXY

11

What trisomies can humans survive?

21, 18 and 13 (18 and 13 die soon after birth)

12

For how many days are sperm motile after insemination?

7 days

13

Where do sperm acquire some motility?

Epididymis

14

When do sperm acquire full motility?

In the female reproductive tract due to uterine secretions

15

What is capacitation?

Hyperactivity of sperm and alteration of the plasma membrane to better bind to the egg.

16

How does the uterine wall induce capacitation?

Ca2+ influx

17

What is the acrosome derived from?

Golgi apparatus

18

What digestive enzymes does the acrosome contain?

hyaluronidase and acrosin

19

What is the function of hyaluronidase and acrosin?

Break down cumulus cells.

20

What is the fast block?

Large Na+ influx, leading to depolarisation- transient

21

What is the slow block/ cortical reaction?

Release of Ca2+ into the egg
Stimulation of cortical granule release, which fuse under the egg surface
Cortical granule contents released into the zona pellucida (b/w cell membrane and vitelline envelope)- permanent.

22

What is the function of the sperm's centriole?

First cleavage.

23

List the steps that follow fertilisation.

Egg complete meiosis II
Second polar body formed
Mitosis of zygote

24

What are blastomeres?

Cells formed after the first division.

25

How many blastomeres are there after day 1?

2

26

How many blastomeres are there after day 2?

4

27

What is the asymmetric hypothesis?

Individual blastomeres are not equivalent.

28

How many blastomeres are there after days 3 and 4?

8

29

What is the morula?

8 blastomere stage

30

At the morula stage, does the embryo increase in size?

No, compaction and cleavage occurs without increase in overall size.