AP BIOLOGY

Detailed explanation-1: -A frameshift variant occurs when there is an addition or loss of nucleotides that shifts the grouping and changes the code for all downstream amino acids. The resulting protein is usually nonfunctional. Insertions, deletions, and duplications can all be frameshift variants.

Detailed explanation-2: -Two frameshift mutations in the CFTR genes cause cystic fibrosis (one involves the insertion of two nucleotides, and the other involves the deletion of one nucleotide).

Detailed explanation-3: -Frameshift mutations are deletions or additions of 1, 2, or 4 nucleotides that change the ribosome reading frame and cause premature termination of translation at a new nonsense or chain termination codon (TAA, TAG, and TGA).