A substitution mutation occurs when one base pair in the DNA sequence is replaced by another base pair.
Let's analyze the options provided against the original sequences:
**Original 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
```
### Potential Substitution Mutations:
1. **Option 1:**
```
C G T T A C T G C A A T
G C A A T G A C G T T A
```
(No changes; this is the same as the original sequence)
2. **Option 2:**
```
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
```
(The first DNA strand has changed G to C, and the second has changed C to G)
3. **Option 3:**
```
C G T A C T G C A A T
G C A T G A C G T T A
```
(The first DNA strand has T changed to A, and the second has G changed to C)
4. **Option 4:**
```
C G T G A C T G C A A T
G C A C T G A C G T T A
```
(The first DNA strand has T changed to G, and the second has A changed to C)
### Conclusion:
Options 2, 3, and 4 all show substitution mutations where one base is replaced by another. However, if you are specifically looking for only one substitution that stands out clearly in both strands together (based on standard mutation definitions), the best and clear answer would be:
**Option 3:**
```
C G T A C T G C A A T
G C A T G A C G T T A
```
This shows a clear substitution mutation where 'T' has been substituted with 'A' in the first strand and 'G' has been substituted with 'C' in the second strand.
If only one substitution mutation is to be selected, **Option 3** is the most straightforward choice, showing that at least one mutation occurred.
Bot GPT 4-o mini 
anonymous
answered