Final answer:
The alteration of the DNA sequence from TAGCTGA to TAGTGA represents a deletion mutation, where a single nucleotide has been removed.
Step-by-step explanation:
If a DNA sequence is altered from TAGCTGA to TAGTGA, the kind of mutation that has occurred is a deletion mutation. This type of mutation means that one or more nucleotides are removed from the DNA sequence. Given that only one nucleotide, 'C', has been removed in the given sequence, it is specifically a single-nucleotide deletion, which can lead to a frameshift if it occurs within a coding sequence. This change can have significant effects on the resulting protein because it may alter the reading frame of the codons that come after the point of deletion.