What type of mutation results when one base is replaced by another?

Base substitution is a type of genetic mutation where one nucleotide base is replaced by another. This process alters the DNA sequence at a specific location, which can potentially affect the corresponding amino acid in a protein, depending on the nature of the substitution. If the change occurs in a gene's coding region, it may lead to a missense or nonsense mutation, impacting protein function or resulting in incomplete proteins.

In contrast, base insertion and base deletion involve the addition or removal of one or more nucleotide bases, which can lead to frameshift mutations. This type of mutation changes the reading frame of the genetic code, affecting downstream amino acids significantly. Chromosomal rearrangement, on the other hand, involves larger alterations such as inversions, duplications, or translocations of chromosome segments, which affect larger sections of the genome rather than individual bases. Thus, base substitution specifically refers to the direct replacement of a single base with another, distinguishing it clearly from the other types of mutations that involve larger alterations or multiple bases.