The DNA sequence reads ACGTTCATT before a mutation occurs. After the mutation, the DNA sequence reads ATCGTTCATT. Which type of mutation occurred?

Compare the sequences: the original is ACGTTCATT, and the mutated sequence is ATCGTTCATT. The mutated sequence has one extra T inserted after the first A, making this an insertion mutation. A substitution would replace one base, while a deletion would remove one.

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