AP BIOLOGY

Detailed explanation-1: -Transition mutations occur when a pyrimidine base (i.e., thymine [T] or cytosine [C]) substitutes for another pyrimidine base or when a purine base (i.e., adenine [A] or guanine [G]) substitutes for another purine base.

Detailed explanation-2: -Such a substitution could: change a codon to one that encodes a different amino acid and cause a small change in the protein produced. For example, sickle cell anemia is caused by a substitution in the beta-hemoglobin gene, which alters a single amino acid in the protein produced.

Detailed explanation-3: -Classical ATT deficiency, caused by mutations in the SERPINA1 gene, commonly appears as lung and liver diseases. The ATT protein works to prevent an enzyme – called elastase – from breaking down other proteins. But other targets, such as proteinase 3 (PR3) and myeloperoxidase (MPO), may also be inactivated by ATT.

Detailed explanation-4: -Substitution, as related to genomics, is a type of mutation in which one nucleotide is replaced by a different nucleotide. The term can also refer to the replacement of one amino acid in a protein with a different amino acid. National Human Genome Research Institute.