Question
Globozoospermia is a genetic condition that leads to male infertility due to the production of abnormal sperm. The diagram compares a normal sperm cell with one produced by a man with globozoospermia.
Why are sperm from males with this condition unable to fertilize eggs?
A. They lack enzymes to digest the follicle cells.
B. They have less genetic material.
C. They have no energy to swim through the oviducts.
D. They fail to reach the plasma membrane of the egg.
▶️Answer/Explanation
Ans. D
Sperm from males with globozoospermia are unable to fertilize eggs because they lack the acrosome, a cap-like covering that contains enzymes that break down an egg’s outer membrane.
Globozoospermia is a rare, severe form of male infertility that affects only males. It’s caused by defects in spermatogenesis, which can lead to abnormal sperm with the following characteristics:
- Round heads
- Abnormal nuclear shape
- Abnormal arrangement of mitochondria
- Absence of an acrosome
- Cytoskeleton defects around the nucleus
- Separation of nuclear membranes
Globozoospermia is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Mutations in the DPY19L2 gene are associated with globozoospermia, and other genes may also be involved.
While globozoospermia was previously considered a sterilizing pathology, some pregnancies have been reported with the help of intracytoplasmic sperm injection (ICSI) and oocyte activation medium.
Question
The image of the pregnancy test shows a positive result. The band indicating pregnancy forms when molecules on the test strip become immobilized after binding to the female hormone HCG.
What are the molecules that bind to HCG?
A. HCG antigens obtained from human plasma
B. HCG antibodies synthesised by human lymphocytes
C. HCG antibodies made by modified plasma cells of small mammals
D. HCG antigens extracted from myeloma cells of mice
▶️Answer/Explanation
Ans. C
A urine pregnancy test detects the presence of human chorionic gonadotropin (hCG) in urine to indicate pregnancy:
How it works
A test strip made of treated nitrocellulose paper contains antibodies that bind to hCG. If hCG is present, it binds to the antibodies, causing the test line to darken. A plus sign, double vertical lines, or the word “pregnant” may appear on the test strip to indicate a positive result. A negative result is indicated by the absence of a colored line or a negative sign.
When to take the test
For best results, take the test first thing in the morning after waking up, as urine is most concentrated at this time.
Factors to consider
Different brands of tests may take different amounts of time to show a result. Some tests have a control window that shows up first to indicate that the test is working. If the control indicator doesn’t activate, the results may be inaccurate.
Question
The diagram shows changes in the uterus lining of a woman throughout her menstrual cycle.
Between which days is she likely to be fertile?
A. 1–6
B. 7–10
C. 11–16
D. 17–21
▶️Answer/Explanation
Ans. C
The menstrual cycle has four phases, and the days when a woman is most likely to be fertile are around ovulation:
Menses
The first day of your period, when bleeding occurs
Follicular
The days between the first day of your period and ovulation, when an egg matures in the ovary
Ovulation
When an egg is released from the ovary and travels towards the uterus, usually around day 14 of a 28-day cycle
Luteal
The days after ovulation, when the lining of the uterus thickens in preparation for pregnancy
The days around ovulation are when a woman is most likely to get pregnant. For the best chance of pregnancy, you should have sex every day or every other day during the five days leading up to ovulation, on the day of ovulation, and the day after ovulation.
The concentration of which hormone peaks sharply triggering ovulation?
A. FSH
B. LH
C. Estrogen
D. Progesterone
Answer/Explanation
Markscheme
B
The diagram shows a section through the male reproductive system. Which structure represents the prostate gland?
Answer/Explanation
Markscheme
C
Question
Which flower structures are indicated by the letters Y and Z?
▶️Answer/Explanation
Ans:D