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)
Responses

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

Answer 1

To identify which sequence shows a substitution mutation, we need to compare the given DNA sequences to find a point where one nucleotide is replaced with another.

Let's review the options to see if any of them display this type of change compared to the original sequence:

1. **Original Sequence:**
- **Top Strand:** C G T T A C T G C A A T
- **Bottom Strand:** G C A A T G A C G T T A

Now, let's examine the response options:

1. **First Option:**
- **Top Strand:** C G T C T A C T G C A A T
- **Bottom Strand:** G C A G A T G A C G T T A
- **Change:** 1st nucleotide in top strand changed from T to C (substitution) and in bottom strand, 2nd nucleotide changed from A to G.

2. **Second Option:**
- **Top Strand:** C G T A C T G C A A T
- **Bottom Strand:** G C A T G A C G T T A
- **Change:** Top strand has changed T to A and bottom strand changed A to T.

3. **Third Option:**
- **Top Strand:** C G T T A C T G C A A T
- **Bottom Strand:** G C A A T G A C G T T A
- **Change:** No substitutions.

4. **Fourth Option:**
- **Top Strand:** C G T G A C T G C A A T
- **Bottom Strand:** G C A C T G A C G T T A
- **Change:** The top strand changes T to G and bottom strand changes A to C, indicating a substitution.

Based on the comparisons, the sequences showing substitution mutations are:

- **First Option**: Shows substitutions T to C (top) and A to G (bottom).
- **Second Option**: Shows substitution T to A and A to T.
- **Fourth Option**: Shows substitution T to G (top) and A to C (bottom).

However, we need to pick one. Among the provided options, **the first option** shows a substitution mutation clearly by changing specific nucleotides in both strands.

So the answer is the **first option**.