Frameshift mutation
A frameshift mutation ( also called a framing error or a reading frame shift ) is a genetic mutation caused by indels ( insertions or deletions ) of a number of nucleotides in a DNA sequence that is not divisible by three . 
<triplet> indel <subj> insertions <obj> has part <subj> deletions <obj> has part <triplet> insertions <subj> indel <obj> part of <triplet> deletions <subj> indel <obj> part of