Unit 2 (K3) - Biology of Controlling Fertility

Question 1

Describe continuous and cyclical fertility.

Answer 1

1. Men have continuous fertility - continually produce sperm in testes.
2. Women have cyclical fertility - women are only fertile a few days during each menstrual cycle. Cyclical fertility leads to a fertile period.

Question 2

Describe the indicators of the fertile period.

Answer 2

Body temperature rises by around 0.5 degrees after ovulation and cervical mucus becomes thin and watery.

Question 3

List 4 treatment of infertility.

Answer 3

1. Stimulating Ovulation
2. Artificial insemination
3. Intra-cytoplasmic sperm injection
4. In vitro fertilisation (IVF)

Question 4

Explain how stimulating ovulation may treat infertility.

Answer 4

1.Drugs can be used to prevent the negative feedback effect of oestrogen on FSH secretion.
2. Other ovulatory drugs mimic the action of FSH and LH. These drugs can cause super ovulation resulting in multiple births or used to collect ova for IVF.

Question 5

What is artificial insemination?

Answer 5

Several samples of semen are collected and the concentrated sample is released into the female’s reproductive tract during her fertile period.

Question 6

When would artificial insemination be a suitable treatment for infertility?

Answer 6

1. If sperm count is low
2. If man is sterile a donor may be used to provide a sample

Question 7

What us intra-cytoplasmic sperm injection?

Answer 7

When the head of the sperm is drawn into a needle and injected directly into the ova to achieve fertilisation.

Question 8

When is Intra-cytoplasmic sperm injection used?

Answer 8

When sperm are low in number or defective.

Question 9

When is IVF used?

Answer 9

When there are blockages in the oviduct.

Question 10

Why is Pre-implantation genetic diagnosis (PGD) used?

Answer 10

This is used to identify single gene disorders and chromosomal abnormalities before implantation.

Question 11

Describe what happens in IVF treatment.

Answer 11

1. Drugs used to stimulate super ovulation.
2. Ovum are surgically removed from the ovaries.
3. Ovum are mixed with sperm in a culture dish.
4. Fertilised eggs are incubated in culture medium for 2-3 days until at least 8 cells.
5. PGD is used.
6. Embryos are transferred to the uterus.
7. Remaining embryos can be frozen and stored in case of second attempt.

Question 12

How do barrier methods of contraception work?

Answer 12

They prevent sperm from entering the uterus.

Question 13

List examples of barrier methods of contraception.

Answer 13

Condom, diaphragm, IUD…

Question 14

How does the oral contraceptive pill work?

Answer 14

This contains a combination of synthetic oestrogen and progesterone which mimics negative feedback preventing the release of FSH and LH therefore preventing follicle maturation and ovulation occurring.

Question 15

How does the mini pill work?

Answer 15

This causes the thickening of cervical mucus which reduces viability of sperm.

Question 16

How does the morning after pill work?

Answer 16

It contains higher doses of progesterone and oestrogen hormones which prevents ovulation or implantation.

Question 17

What is a tubal ligation?

Answer 17

This is the cutting and tying of the oviducts to prevent ova from meeting sperm.

Question 18

What is a vasectomy?

Answer 18

This involves the cutting and tying of the sperm ducts which prevents sperm from being released.