AP BIOLOGY

Detailed explanation-1: -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.

Detailed explanation-2: -Types of Substitution Mutations Within the four nucleotides, there are two types: the purines and pyrimidines. Adenine (A) and guanine (G) are both purines, while cytosine (C) and thymine (T) are pyrimidines. If a purine changes to a purine, the substitution mutation is considered a transition.

Detailed explanation-3: -Substitution mutations can be good, bad, or have no effect. They cause three specific types of point mutation: silent, missense, and nonsense mutations. A silent mutation is one where the function of the protein is not changed. A missense mutation codes for the wrong protein.

Detailed explanation-4: -Missense: A missense variant is a type of substitution in which the nucleotide change results in the replacement of one protein building block (amino acid) with another in the protein made from the gene. The amino acid change may alter the function of the protein.

Detailed explanation-5: -Base Substitutions Single base substitutions are called point mutations, recall the point mutation Glu—–> Val which causes sickle-cell disease. Point mutations are the most common type of mutation and there are two types.