Question

many different types of errors can occur during dna synthesis. most dna synthesis errors are caught and repaired by dna polymerase. sometimes, an error is missed and becomes a permanent dna mutation. below is a diagram showing one such dna mutation. which statement best describes the mutation shown above? a a silent mutation results in the insertion of a different amino acid. b a substitution occurs with an adenine base. c a deletion of a cytosine base occurs. d a base is inserted into one strand of the dna.

Explanation:

Compare the original DNA sequence "CACGATCAG" and the mutated DNA sequence "CACGTTCAG". The fourth base in the original is "A" (adenine), and in the mutated one, it's "T". This is a substitution mutation where adenine is replaced. A silent mutation doesn't change the amino - acid (not the case here). There's no deletion (C is wrong) or insertion (D is wrong) as the number of bases remains the same.

Answer:

B. A substitution occurs with an adenine base.