Counting the days
318 words over 30 numbered lines, then 7 parts worth 12 marks (Modular Unit 2 (4WBI2) style, 12–13 marks). Read the article, answer each part, then open its mark scheme and set your mark.
Illustrative article written for Scholar Lab, not a Pearson text. The biology is real; the studies, people and figures are invented or rounded for practice unless a source is named.
Counting the days
About one in seven couples who want a baby have difficulty conceiving,
and some have been trying for several years. To help them, doctors
first need to understand what is happening during the woman’s
menstrual cycle, which usually lasts about 28 days and is coordinated
by four hormones.
At the start of the cycle, the pituitary gland in the brain releases
follicle-stimulating hormone, FSH. This causes an egg to mature inside
a follicle in one of the ovaries. The follicle releases oestrogen,
which makes the lining of the uterus grow thicker. Rising oestrogen
also causes a surge of luteinising hormone, LH, from the pituitary
gland. The surge of LH triggers ovulation, the release of the egg from
the ovary.
After ovulation, the empty follicle releases progesterone, which
maintains the thick lining of the uterus. If the egg is fertilised,
the nucleus of a sperm fuses with the nucleus of the egg to form a
zygote. The zygote divides to form an embryo, which may implant in the
lining. If there is no pregnancy, progesterone falls and the lining
breaks down.
Figure 1 shows illustrative concentrations of FSH and LH in the blood
of a woman during one cycle. Blood tests and home test kits that
detect the LH surge can help a couple to know when the woman is most
likely to be fertile.
If a couple still cannot conceive, they may be offered in vitro
fertilisation, or IVF. The woman is given injections of FSH so that
several eggs mature at the same time. The eggs are collected and mixed
with sperm in a dish. A few days later, one or two embryos are placed
in her uterus. At one illustrative clinic, 360 embryos were
transferred in a year and 99 of these resulted in a pregnancy. Each
embryo that is transferred has a chance of implanting, but many do
not, so couples may need several attempts.
Figure 1 Concentrations of FSH and LH in the blood during one menstrual cycle
Read the article and study the figure. Use the information in the article and your own knowledge to answer the questions. The lines in brackets show where to look; select them to highlight the text.
Use the information in the article and your own knowledge to answer the questions. The lines in brackets show you where to look; select them to highlight the text.
State what is meant by the term ovulation.
(1)Name the gland that releases FSH and LH.
(1)Use Figure 1 to give the day on which ovulation is most likely to happen.
(1)Describe the roles of FSH and LH in the menstrual cycle.
(3)Explain why the lining of the uterus breaks down if there is no pregnancy.
(2)Calculate the percentage of embryos transferred at the clinic that resulted in a pregnancy.
(2)Suggest why women having IVF are given injections of FSH.
(2)Total for this question: 12 marks
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