This mutation results from the insertion of two nucleotides into the original sequence which causes the reading frame of the sequence to change this kind of mutation is known as

The answer would be frameshift mutation.

The frameshift mutation happens when insertion or deletion of a number of nucleotides that is not multiple of 3. The result will definitely cause a problem in the reading sequence.
In this case, there are insertions of two nucleotides and two is not multiple of 3.

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