SAT Subject Biology Practice Question 31: Answer and Explanation

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Question: 31

5. Which of these mutations in a gene will MOST LIKELY result in a shortened protein with a long sequence of substituted amino acids?

A. Missense substitution of one nucleotide
B. Insertion of two nucleotides
C. Deletion of three nucleotides
D. Silent substitution of four nucleotides
E. Nonsense substitution of five nucleotides

Correct Answer: B


The insertion of two nucleotides will shift the reading frame of all the codons "downstream" of the mutation, resulting in a series of mis-sense codons and eventually a nonsense (stop) codon.

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