Answer:
insertion mutation
Step-by-step explanation:
a substitution mutation only changes one thing, but an insertion mutation changes everything after the point of insertion. The insertion pushes everything back, causing a chain effect
lets say i have the sentence "I have a dog"
a substitution mutation might change it to "K have a dog", seems kinda bad, but not as bad as "K Ihav e ado g" (result of insertion of K at beginning)