Molecular Biology and Genetics MCQ Questions with answers and solutions Page 6

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Q. A mutation in a gene that codes for a polypeptide results in a variant polypeptide that lacks the last three amino acids. What type of mutation is this?

(A) Synonymous mutation
(B) Nonsense mutation
(C) Missense mutation
(D) Silent mutation

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✅ Correct Answer: (B) Nonsense mutation

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📊 Molecular Biology and Genetics

Q. Topological winding number of a 2.0 kb covalently closed circular DNA was found to be 191 with a writhing number of -4. Hence, its linking number and the number of base pair per turn when the molecule is laid flat on the surface is . . . . . . . . and . . . . . . . ., respectively.

(A) 187, 10.69
(B) 195, 10.25
(C) 200, 10.00
(D) 187, 10.50

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✅ Correct Answer: (A) 187, 10.69

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📊 Molecular Biology and Genetics

Q. PKU is one of the best-known hereditary disorders in amino acid metabolism. The defect is attributed to a lesion in one of the following enzymatic activities:

(A) Phenylalanine ammonia lyase
(B) Phenylalanine hydroxylase
(C) Tyrosine hydroxylase
(D) Phenylalanine transaminase

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✅ Correct Answer: (B) Phenylalanine hydroxylase

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Q. A truncated polypeptide is synthesized due to a nonsense mutation. Where would you introduce another mutation to obtain a full-length polypeptide?

(A) Ribosomal protein gene
(B) Transfer RNA gene
(C) DNA repair gene
(D) Ribosomal RNA gene

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✅ Correct Answer: (B) Transfer RNA gene

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Q. Diploid Drosophila has eight chromosomes. Which one of the following terms should not be used to describe Drosophila with sixteen numbers of chromosomes?