NUMS — Medical & Dental Entry Test
Take the NUMS Biology — Reproduction, Inheritance, Evolution and Biotechnology (Set 1): 30 multiple-choice questions (40 minutes) with instant scoring and…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. A sudden surge of which hormone around day 14 of the menstrual cycle triggers ovulation?
Answer: D. Luteinising hormone (LH)
Explanation: Rising oestrogen exerts positive feedback on the pituitary, causing an LH surge that ruptures the mature follicle.
Q2. After ovulation, the corpus luteum secretes progesterone. If fertilisation does not occur, the corpus luteum degenerates, leading to:
Answer: B. A fall in progesterone and shedding of the endometrium (menstruation)
Explanation: Without hCG from an embryo, the corpus luteum regresses; falling progesterone causes the endometrium to break down.
Q3. Pregnancy tests detect human chorionic gonadotropin (hCG). Its function in early pregnancy is to:
Answer: C. Maintain the corpus luteum so that progesterone secretion continues
Explanation: hCG from the trophoblast keeps the corpus luteum active until the placenta takes over progesterone production.
Q4. In males, testosterone is produced by the ______ under the influence of ______.
Answer: C. Interstitial (Leydig) cells; LH
Explanation: LH (ICSH) stimulates Leydig cells to make testosterone; FSH acts on Sertoli cells to support spermatogenesis.
Q5. From one primary spermatocyte, how many sperms are produced, compared with the number of ova from one primary oocyte?
Answer: B. 4 sperms and 1 ovum
Explanation: Meiosis of a spermatocyte gives four spermatids; oogenesis gives one ovum plus polar bodies due to unequal cytoplasmic division.
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Q6. Which event of meiosis I produces genetic variation by exchanging segments between homologous chromatids?
Q7. A pea plant heterozygous for tall stem (Tt) is crossed with a dwarf plant (tt). What proportion of offspring will be dwarf?
Q8. Two plants heterozygous for two unlinked genes (AaBb × AaBb) are crossed. What fraction of offspring will show both recessive traits?
Q9. A cross between red-flowered and white-flowered snapdragons gives all pink offspring. When the pink plants are self-crossed, the F₂ ratio is:
Q10. A man with blood group A (genotype IᴬIᴼ) marries a woman with group B (IᴮIᴼ). Which blood groups are possible in their children?
Q11. A woman who is a carrier of haemophilia marries a normal man. What is the probability that their son will be haemophilic?
Q12. Red–green colour blindness is much more common in men than in women because:
Q13. Human skin colour shows a continuous range of shades controlled by several genes with additive effects. This is an example of:
Q14. Two genes located very close together on the same chromosome usually do not assort independently. They are said to be:
Q15. Down syndrome usually results from non-disjunction producing a gamete with an extra chromosome 21. The karyotype of the affected person is:
Q16. Bacteria grown for many generations in ¹⁵N medium are transferred to ¹⁴N medium. After TWO rounds of replication, the DNA forms two equal bands: one of intermediate density and one light. This result supports:
Q17. A mutation changes a codon from UAU (tyrosine) to UAA. What is the likely result?
Q18. Insertion of a single nucleotide near the start of a gene is usually more harmful than a single base substitution because it:
Q19. Restriction endonucleases are useful in genetic engineering because they:
Q20. Which enzyme is used to seal the sugar–phosphate backbone when a gene is inserted into a plasmid?
Q21. In PCR, the DNA polymerase used (Taq polymerase) is obtained from a thermophilic bacterium because:
Q22. Starting with one DNA molecule, how many copies are theoretically present after 5 cycles of PCR?
Q23. In gel electrophoresis, DNA fragments move towards the positive electrode, with smaller fragments travelling farther. This is because DNA:
Q24. Human insulin produced by genetically modified bacteria is preferred over animal insulin because it:
Q25. Darwin's theory of natural selection is based on which key observation?
Q26. Bacteria in a hospital become resistant to an antibiotic after years of use. The best explanation is:
Q27. The forelimbs of a human, a whale and a bat have the same basic bone pattern but different functions. These are:
Q28. Wings of a butterfly and wings of a bird perform the same function but have different structures and origins. They illustrate:
Q29. In a population in Hardy–Weinberg equilibrium, the frequency of a recessive allele is 0.3. What is the expected frequency of heterozygotes?
Q30. Lamarck's explanation that giraffes have long necks differs from Darwin's because Lamarck proposed that: