Quick revision: every question with its correct answer. For the full explanation, open the test and tap View Solution.
4.2 Mutagens & Their Detection — Test 1
Q1. Frameshift mutations are characteristically caused by the agent:✓ Proflavin (an acridine dye)
Q2. UV radiation primarily induces the formation of:✓ Pyrimidine (thymine) dimers
Q3. 5-Bromouracil, a base analogue, is incorporated in place of thymine and most often induces:✓ T:A → C:G transition
Q4. Which of the following is a DNA intercalating agent?✓ Acridine orange
Q5. Deamination of adenine produces:✓ Hypoxanthine
Q6. Deamination of 5-methylcytosine yields:✓ Thymine
Q7. Which of the following is NOT a DNA-depurinating agent?✓ Methyl ethane sulphonate
Q8. Which mutagen is most likely to cause a single amino-acid change (a point substitution)?✓ Ethyl methane sulphonate (EMS)
Q9. 2-Aminopurine induces mutation by:✓ Causing base-pair substitution (it is a base analogue)
Q10. A potent alkylating mutagen frequently used in genetic screens is:✓ Nitroso-ethyl urea (ENU)
Q11. The randomness of mutation (pre-adaptive, not directed by selection) was demonstrated by:✓ Luria and Delbrück
Q12. The Luria–Delbrück fluctuation test and Lederberg replica-plating experiments together demonstrate:✓ Pre-selection (random) mutation
Q13. Mutations that arise in the absence of any known mutagen are called:✓ Spontaneous mutations
Q14. Mutations occurring in body cells that do not form gametes are called:✓ Somatic mutations
Q15. The Ames test is used primarily to determine the:✓ Mutagenicity of a chemical
Q16. Three compounds are tested: M1 reversions are induced by base analogues; M2 by base analogues and other substitution mutagens; M3 only by acridines. Their likely natures are:✓ M1 transition, M2 transversion, M3 insertion/frameshift
Q17. Compound X mutations are reverted by 5-bromouracil and EMS; compound Y mutations are reverted by acridine orange. The natures are:✓ X = base substitutions (transitions); Y = insertions/deletions (frameshifts)
Q18. An aspartate codon (GAU/GAC) is changed to alanine (GCN), a change reverted only by reactive oxygen species. The mutation is a:✓ Transversion
Q19. Nitrous acid is mutagenic mainly because it causes:✓ Oxidative deamination of bases, leading to transitions
Q20. Match each mutagen with its mechanism and select the correct option.✓ A-ii, B-i, C-iv, D-iii