Fertilisation and development

Question 1

What is syngamy?

Answer 1

Gamete fusion

Question 2

How does the sperm capacitate in the female reproductive tract?

Answer 2

1) Acrosomal reaction
- Holes in the acrosomal cap
- Allow enzymes which erode the surface of the egg out

2) Motility changes

Question 3

What makes the male pronucleus?

Answer 3

• The head of the sperm

- Must decondense

Question 4

What makes the female pronucleus?

Answer 4

When the egg completes meiosis after fertilisation

Question 5

Where does the zygote attach to?

Answer 5

The endometrium

Question 6

Why do females mature earlier than males?

Answer 6

Gestation time is one day longer (266 days)

Question 7

What determines the gender of the embryo?

Answer 7

Y bearing sperm from the male

Question 8

Where do gonads develop?

Answer 8

In gonal ridges either side of the midline

Question 9

What are oogonia and how do they divide?

Answer 9

Undifferentiated germ cells of the female which give rise to oocytes

Devide by mitosis

Question 10

What causes oogonia to derive into oocytes?

Answer 10

MIS (meosis inducing substance) from the mesenepheric ducts

Question 11

Where are mesenepheric ducts present?

Answer 11

in both males and females but males also produce MPS (meosis preventing substance) from the testes cords in higher amounts

Question 12

How do spermatogonia divide?

Answer 12

By mitosis`

Question 13

What gene induces the formation of testes?

Answer 13

SRY gene produced by the sertoli cells

Question 14

What is AMH?

Answer 14

Anti mullerian hormone, released from the testes

Question 15

What is the SOX9 gene?

Answer 15

• Gene involved in the long term maintenance of the male development pathway
• Increases a few days after SRY activated in males
• Declines in females

Question 16

What happens if there is a mutation in SOX9 in females?

Answer 16

Can direct the females down the male pathway

Question 17

What happens in the absence on Jmj1a in males?

Answer 17

• SRY not expressed

- XY is phenotypically female

Question 18

What does 5 alpha reductase do and what happens if there is a deficiency in it?

Answer 18

• Converts testosterone into 5-DHT (dihydroxytestosterone) a more active version
• If deficiency, lack male genetalia

Question 19

What is testicular feminisation syndrome and when does it occur?

Answer 19

• Karyotype 46/XY
• Normal male genotype but female phenotype, due to low levels of cytosolic carrier protein
• Testosterone cant work but normal levels produced
• Female phenotype due to unopposed action of small amounts of oestrogen from the testes and adrenal cortex

Question 20

What duct is degenerated in the male at 10 weeks?

Answer 20

The mullerian duct

Question 21

What duct is degenerated in the female at 10 weeks?

Answer 21

The wolffian duct