Answer: There is addition or deletion of one or more nucleotides in a DNA sequence which alters the original reading frame of the DNA.
Explanation: In frameshift mutation, one or more nucleotides is added to or deleted from a DNA sequence resulting in altered reading frame.
For example, a DNA sequence having an original reading frame: (ACT)(GAG)(CCG)(TAT)(G is changed to (ACG)(AGC)(CGT)(ATG) when a thymidine nucleotide at position 3 is deleted. This frameshift mutation will result in the synthesis of complementary DNA strand with an altered nucleotide sequence during replication and an RNA sequence with an altered sequence during transcription and a protein with an altered amino acid sequence.