Answer:
Sequence A
CGTTACTGCAAT to CGTGACTGCAAT
Explanation:
Mutation refers to any change, whether big or small, that occurs in the nucleotide sequence of a DNA/gene. This change can either be caused by replicational errors or induced by mutagens. Mutation can be of different types depending on the effects on the affected organism (mutant).
A substitution mutation is a kind of mutation in which one or more nucleotide base is replaced by another in a sequence. This is the case here as the
original sequence: CGTTACTGCAAT
Mutated sequence: CGTGACTGCAAT
The fourth base, T has been replaced by G in the upper strand of the DNA sequence.