NUMS — Medical & Dental Entry Test
Take the NUMS Biology — Reproduction, Inheritance, Evolution and Biotechnology (Set 3): 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 heterozygous tall pea plant (Tt) is crossed with a dwarf plant (tt). What fraction of the offspring is expected to be dwarf?
Answer: B. 1/2
Explanation: Tt × tt gives 1 Tt : 1 tt.
Q2. Two heterozygous parents (AaBb × AaBb) are crossed with independent assortment. What fraction of offspring is aabb?
Answer: D. 1/16
Explanation: (1/4)(1/4) = 1/16.
Q3. In AaBb × AaBb, what fraction of the offspring shows the dominant phenotype for both traits?
Answer: D. 9/16
Explanation: The 9:3:3:1 ratio gives 9/16 A_B_.
Q4. A colour-blind man marries a normal woman whose father was colour-blind. What is the probability that their son is colour-blind?
Answer: C. 1/2
Explanation: The woman is a carrier (X^C X^c); half of her sons receive X^c.
Q5. A haemophilic father and a normal homozygous mother have children. Which statement is correct?
Answer: C. All daughters are carriers and all sons are normal
Explanation: Daughters receive the father's X^h and are carriers; sons receive the father's Y and the mother's normal X.
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Q6. A child has blood group O. Her mother is group A and her father is group B. What are the parents' genotypes?
Q7. A man of group AB marries a woman of group O. Which blood groups are possible among their children?
Q8. A red-flowered snapdragon (RR) crossed with a white-flowered one (rr) gives pink F₁ (Rr). If the F₁ are selfed, the phenotypic ratio of the F₂ is:
Q9. In a cross between two plants heterozygous for genes located close together on the same chromosome, the offspring show mostly parental types. This indicates:
Q10. In a test cross, 42 parental and 8 recombinant offspring were obtained. The recombination frequency is:
Q11. Down syndrome arises from nondisjunction in meiosis, producing a gamete with 24 chromosomes. How many chromosomes does the zygote have after fertilisation with a normal gamete?
Q12. A female with a 45,X karyotype has:
Q13. The risk of a trisomy 21 child rises with maternal age mainly because:
Q14. Which event in meiosis I is responsible for the recombination of linked genes?
Q15. A cell with 2n = 8 chromosomes undergoes meiosis. How many chromosomes does each daughter cell have at the end of meiosis II?
Q16. How many different gamete combinations are possible from a cell with n = 3 chromosome pairs (ignoring crossing over)?
Q17. In a human male, FSH acts on:
Q18. Secondary oocyte completes meiosis II only if:
Q19. The corpus luteum persists in early pregnancy because:
Q20. Which step in DNA replication joins Okazaki fragments?
Q21. DNA replication is called semi-conservative because:
Q22. A segment of DNA template reads 3′–TAC GGA–5′. The mRNA produced is:
Q23. A nonsense mutation changes a codon for an amino acid to UAA. The result is:
Q24. Deletion of one nucleotide from the middle of a gene is likely to produce:
Q25. Restriction enzymes cut DNA at:
Q26. In gel electrophoresis, DNA fragments move towards the:
Q27. Which enzyme is essential for PCR and is stable at high temperature?
Q28. Starting with one DNA molecule, how many copies are present after 10 cycles of PCR (ideal)?
Q29. A recessive allele has a frequency of 0.3 in a population at Hardy–Weinberg equilibrium. What proportion of individuals are carriers (heterozygous)?
Q30. The industrial melanism of peppered moths is an example of: