Answer: A frameshift mutation can be caused either by an insertion or deletion of a nucleotide in a DNA sequence.
Explanation: A frameshift mutation is a type of mutation in which one or more nucleotides are either inserted or deleted in a nucleotide sequence. When a nucleotide in inserted or deleted, it results in the production of an mRNA with an altered reading frame. The nucleotide sequence in an mRNA are read in triplets known as codons. In the reading frame, the nucleotides are read in triplets with one overlapping with the order, but once a nucleotide is added or deleted, the reading frame changes and this will result in the incorporation of wrong amino acids from the point of mutation to the end of the sequence.