2C The Biology Of Controllin Fertility

Question 1

Is female fertility cyclical or continuous?

Answer 1

Cyclical. Females are only fertile for 2-3 days per month. Men are continually fertile.

Question 2

What indicators can be used to calculate the fertile period of a female?

Answer 2

• Her temperature. It rises between 0.2-0.5 degrees under the action of progesterone.
• Mucus consistency- During the fertile period, the mucus is thin and watery to allow the sleek to enter the female reproductive system.
• After ovulation, the mucus gradually becomes thick and sticky (under the action of progesterone), showing that the system has returned to the infertile phase.

Question 3

How can female infertility be treated?

Answer 3

• Ovulation drugs mimic the action of FSH and LH. These drugs can cause super ovulation that can result in multiple births or be used to collect ova for vitro fertilisation (IVF) programmes.
• Stimulating ovulation. Ovulation stimulate by drugs that percent the negative feedback of oestrogen on FSH secretion.

Question 4

Name two processes which females can undergo to fall pregnant without having sexual intercourse.

Answer 4

Artificial insemination or IVF.

Question 5

What does artificial insemination involve?

Answer 5

Collecting samples of the male’s sperm over time (preserved by freezing) and depositing them in the female reproductive system (artificially). The act of sexual intercourse does not take place.

Question 6

Under what circumstance can artificial insemination he used?

Answer 6

If male’s have a low sperm count. If a man is sterile, a donor who has a normal sperm can be used.

Question 7

Describe intra-cytoplasmic sperm injection (ICIS)

Answer 7

If mature sperm are defective or very low in number ICSI can be used:
•The head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation.

Question 8

Describe the process of IVF.

Answer 8

1) The female is given hormonal treatment to stimulate multiple ovulation.
2) Eggs are removed from her ovary.
3) The eggs and sperm are mixed in a culture dish of nutrient medium to allow fertilisation to occur.
4) The eggs are incubated in the medium for 2-3 days to allow cell division to occur and form embryos of 8 or more cells.
5) Two or three embryos are chosen and then inserted via the vagina into the mother’s uterus.
6) The remaining embryos are frozen and stored in case a second attempt at implantation is required.

Question 9

Before the embryos are inserted in the vagina of the female, what can be removed from the embryo and why?

Answer 9

Cells to be tested for genetic abnormalities.

Question 10

What form can the tests in embryonic cells be in?

Answer 10

• Pre-implantation genetic screening (PGS) which is a non-specific approach that checks the embryo for single gene disorders and common chromosomal abnormalities in general.
• Pre-implantation genetic diagnosis which is a specific approach that is used to check for a known chromosomal or gene defect.

Question 11

What can IVF and PGD identify within the ovaries?

Answer 11

Single gene disorders and chromosomal abnormalities.

Question 12

What are the physical barriers of contraception?

Answer 12

• Barrier methods such as condoms
• Avoiding fertile periods
• IUD’s
• Sterilisation procedures

Question 13

Why are chemical contraceptions successful?

Answer 13

• Some prevent implantation (‘morning after pills’)

* Cause thickening of cervical mucus (‘progesterone only pill’)