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Look at the DNA sequence.

C G T T A C T G C A A T
G C A A T G A C G T T A
Which sequence shows a substitution mutation?

(1 point)
Responses

C G T T A C T G C A A T
G C A A T G A C G T T A
C G T T A C T G C A A T G C A A T G A C G T T A

C G T C T A C T G C A A T
G C A G A T G A C G T T A
C G T C T A C T G C A A T G C A G A T G A C G T T A

C G T A C T G C A A T
G C A T G A C G T T A
C G T A C T G C A A T G C A T G A C G T T A

C G T G A C T G C A A T
G C A C T G A C G T T A

1 answer

A substitution mutation occurs when one base pair in a DNA sequence is replaced with another base pair. Let's compare the sequences given in the responses to identify which one has a substitution mutation.

  1. First Response:

    • Original: C G T T A C T G C A A T
    • Mutated: G C A A T G A C G T T A
    • Comparison: No substitution; sequence is completely different.

  2. Second Response:

    • Original: C G T T A C T G C A A T
    • Mutated: C G T C T A C T G C A A T
    • Comparison: The second base has changed from T to C. This indicates a substitution mutation.

  3. Third Response:

    • Original: C G T T A C T G C A A T
    • Mutated: C G T A C T G C A A T
    • Comparison: The fourth base has changed from T to A. This indicates a substitution mutation.

  4. Fourth Response:

    • Original: C G T T A C T G C A A T
    • Mutated: C G T G A C T G C A A T
    • Comparison: The third base has changed from T to G. This indicates a substitution mutation.

Based on the analysis, the second, third, and fourth responses all show substitution mutations. However, if you can only select one, the clear substitution in the second response (T to C) is the simplest to identify and verify.

So the answer is the second option: C G T C T A C T G C A A T (showing a substitution mutation of T to C).