You are part of a group of researchers working on determining the genetic basis for early onset Osteoporosis. Using data from subjects in Iceland, you are able to identify where the mutation is located. The target gene in unaffected people produces the amino acid sequence Pro-Met-Glu-Arg-Asp. In individuals with the mutation, the protein produced has a sequence of Pro-Met- then stops. What type of mutation is this?
A. Nonsense mutation
B. Insertion mutation
C. Inversion mutation
D. Missense mutation