A frame shift mutation could result from

A frame shift mutation is a type of genetic mutation that occurs when the number of nucleotides inserted or deleted is not a multiple of three. This alters the reading frame of the genetic code and changes the amino acid sequence of the resulting protein.

An insertion or deletion of a single nucleotide in the DNA sequence can cause a frame shift mutation, whereas a base substitution would not, as it only changes one nucleotide in the sequence.

Therefore, either an insertion or a deletion of a base could result in a frame shift mutation.