A substitution mutation occurs when one nucleotide in a DNA sequence is replaced by another nucleotide.
Let's analyze the provided sequences:
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First option:
- 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
- Change: T -> G (substitution)
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Second option:
- 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
- Change: T -> C (substitution)
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Third option:
- 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
- Change: T -> A (substitution)
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Fourth option:
- Original: C G T T A C T G C A A T
- Mutated: C G T T A C T G C A A T
- No changes (no mutation)
Among these options, the first, second, and third have substitution mutations.
However, typically, the question is asking for only one instance. If you need to select one, the simplest and most clear example would be any of the first three options.
If your answer had to be unique, you might pick one:
- First option: C G T G A C T G C A A T (substitution T -> G).
Please select based on your specific preference or criteria if you need to choose only one.