Question

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)

Answer 1

A substitution mutation occurs when one nucleotide in the DNA sequence is replaced by another. Let's compare the two sequences provided:

1. Sequence 1:
C G T T A C T G C A A T

2. Sequence 2:
G C A A T G A C G T T A

Now, we can look for differences between these two sequences:

- In the first position, C (Sequence 1) is replaced by G (Sequence 2).
- In the second position, G (Sequence 1) is replaced by C (Sequence 2).
- In the third position, T (Sequence 1) is replaced by A (Sequence 2).
- In the fourth position, T remains the same.
- In the fifth position, A remains the same.
- In the sixth position, C (Sequence 1) is replaced by G (Sequence 2).
- In the seventh position, T (Sequence 1) is replaced by A (Sequence 2).
- In the eighth position, G remains the same.
- In the ninth position, C remains the same.
- In the tenth position, A remains the same.
- In the eleventh position, A remains the same.
- In the twelfth position, T (Sequence 1) is replaced by A (Sequence 2).

Since almost every position differs and the sequences do not match each other closely, it indicates that a substitution mutation has taken place at multiple points.

However, if we must choose just one example of a substitution mutation, we can pick the first difference from the sequences:

From C to G in the first position of Sequence 1 vs Sequence 2.

So, the sequence showing a substitution mutation would begin with "C" in Sequence 1 and is "G" in Sequence 2 at the first nucleotide position.