SAT Subject Biology Practice Question 157: Answer and Explanation

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Question: 157

7. A genetic mutation that adds a nucleotide to a protein-coding sequence of DNA creates an early stop codon. How will this influence the resulting protein?

A. The primary structure of the protein will be unaffected.
B. The secondary structure of the protein will be unchanged.
C. The protein will not be translated at all.
D. The protein will be complete but function abnormally.
E. The protein will be synthesized normally up to the mutation.

Correct Answer: E

Explanation:

A stop codon terminates amino acid translation. If this occurs before the true end of a protein-coding sequence, the protein up to that point will be formed normally but then be truncated as an incomplete protein.

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