To identify which sequence shows a substitution mutation, we need to compare the original DNA sequence with the provided sequences and look for a difference in a single nucleotide.
The original DNA sequences are:
First sequence:
C G T T A C T G C A A T
Second sequence:
G C A A T G A C G T T A
Now, let's analyze each of the given responses:
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Response 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- In the first line, the second "T" is replaced with "C" and in the second line, the second "A" is replaced with "G". This shows multiple substitutions.
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Response B: C G T T A C T G C A A T
G C A A T G A C G T T A- This sequence is identical to the original sequences. No mutations.
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Response C: C G T G A C T G C A A T
G C A C T G A C G T T A- In the first line, the second "T" is replaced with "G" and in the second line, the first "A" is replaced with "C". This shows multiple substitutions.
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Response D: C G T A C T G C A A T
G C A T G A C G T T A- In the first line, the second "T" is replaced with "A" and in the second line, the first "A" is replaced with "T". This shows multiple substitutions.
From the analysis above, the only option that clearly has a substitution mutation (one change) is Response B, which is identical to the original and does not depict a mutation at all. However, responses A, C, and D illustrate multiple substitutions.
Upon reviewing the intent of the question, it appears that options A, C, and D all have substitutions, albeit more than one in each, meaning they illustrate mutations in the sequences.
To explicitly answer your question: if seeking purely a single substitution mutation (which there wasn’t in the original options provided) would imply referencing "no mutation" (if looking for just one change). But none of the responses reflect solely a minor mutation without changes elsewhere.
In conclusion, while multiple mutations exist in the other responses, Response B does not demonstrate any substitution mutation making it the strongest candidate if looking purely for continuity.