Menstrual Cycle, Fertility and Genetics

Question 1

(2) Explain how changes in the levels of hormones result in ovulation.

Answer 1

• rising oestrogen levels (1)
• (stimulate production of) LH (1)
• (LH) levels increase / when it reaches a set level / peaks (which causes ovulation) (1)

Question 2

(2) Explain what happens to the uterus lining if the egg cell is fertilised.

Answer 2

• Uterus lining maintained/ thickened (more) (1)
With one of:
• Because progesterone levels maintained / progesterone is still produced
• So that the embryo can embed on it / So that the uterus lining can supply the embryo with nutrients

Question 3

(4) Use the diagram to help explain the body’s hormonal response to dehydration.

Answer 3

• (dehydration detected by) osmoreceptors/hypothala mus (1)
• pituitary gland (1)
• (releases more) ADH (1)
• ADH acts on the nephron/collecting duct/tubules (1)
• making the {collecting duct/tubules/nephron} more permeable (1)
• so more water is reabsorbed (by the body/blood) (1)

Question 4

(1) Describe the effect of high levels of progesterone on the uterus lining during pregnancy.

Answer 4

uterus lining remains thick/uterus lining continues to grow (1)

Question 5

(6) Explain how the menstrual cycle is controlled by hormones and negative feedback.

Answer 5

Stages and hormones
• menstrual cycle consists of menstruation, uterus lining thickening and ovulation
• hormones involved in the menstrual cycle are oestrogen, progesterone, FSH and LH
Role of the hormones
• FSH stimulates the follicles to mature
• follicles secrete oestrogen
• oestrogen is responsible for the repair of the uterus wall
• high levels of oestrogen stimulate the release of LH
• LH triggers ovulation
• corpus luteum produces progesterone
• progesterone maintains the lining of the uterus
Control mechanisms
• oestrogen inhibits the production of FSH
• progesterone inhibits the production of LH
• progesterone inhibits the production of FSH
• menstruation is triggered by low levels of oestrogen and progesterone
• Low progesterone levels cause FSH to be released

Question 6

(1) An acrosome contains

Answer 6

enzymes to help get through the membrane of the egg cell

Question 7

(1) State why egg cells have a large amount of cytoplasm.

Answer 7

to supply / contain (a large amount of) nutrients / energy

for the zygote / embryo

Question 8

(2) Complete the diagram by writing the sex chromosomes in the egg cells, sperm cells, male zygote and female zygote.

Answer 8

Gametes correctly labelled X X X Y (1) Female zygote X X , Male zygote X Y (1)

Question 9

(1) The hormone that stimulates the maturation of follicles in the ovary is

Answer 9

FSH

Question 10

(1) Ovulation during pregnancy is prevented by high levels of

Answer 10

progesterone

Question 11

(2) Explain one disadvantage of treating infertility by using hormones to
stimulate ovulation.

Answer 11

more than one egg {released /
fertilised }(1)
multiple birth / pregnancy (1)
increased risk of complications
for mother/babies (1)
OR
women affected by side effects
(1)

Question 12

(2) Explain why the male offspring from A and B do not have haemophilia.

Answer 12

they did not inherit the (haemophilia) allele (1)
(allele is) located on X chromosome (1)
males receive X chromosome from their mother/Y chromosome from father (1)
B is homozygous dominant/ neither X chromosome from B has the allele for haemophilia (1)