Mutation by Substitution

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Whereas in genetic mutation by insertion extra base pairs are inserted into the DNA, in mutation by substitution one base in the sequence is replaced for another.

Whereas in genetic mutation by insertion extra base pairs are inserted into the DNA, mutation by substitution occurs when one base in the sequence is replaced for another.

Unlike genetic mutation by insertion, where extra base pairs are inserted into the DNA, one base in the sequence is replaced for another in mutation by substitution.

Unlike genetic mutation by insertion, where extra base pairs are inserted into the DNA, mutation by substitution replaces one base in the sequence with another.

Unlike the case of extra base pairs inserted into the DNA, which is genetic mutation by insertion, in mutation by substitution one base in the sequence is replaced with another.

Review: Mutation by Substitution

Explanation

Creating a filter: supposing that we read the prompt and don't find any errors, we can proceed to choice (B) and come back to (A) later.

Finding objective defects: choice (B) is defective. The use of the word "when" is inaccurate here, because we are talking about how these mutations happen, not when. The comparison is also needlessly nonparallel. Choice (C) has a non-parallel comparison between "mutation by insertion" and "one base," so we eliminate choice (C). Choice (D) uses the word "where" incorrectly, because we aren't talking about location, and it attributes action to "mutation by substitution" rather than define the phenomenon. Choice (E) compares "case" with a non-case. The correct answer is (A).

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Mutation by Substitution