Terms Based on DNA Sequence Changes

Point Mutation. A mutation occurs at a DNA base in which the base is mutated to another base, is deleted, or another base is inserted. 

Base Substitution Mutation. A mutation where one base is mutated to a different base. That is, a DNA base is replaced by one of the other three bases. 

Transition Mutation. Occurs when one purine is mutated to another purine or one pyrimidine is mutated to another pyrimidine, that is, A G, G - A, C - T, and T — C. 

Frameshift Mutation. Deletion or insertion of a base or bases that alters the reading frame of the gene. In contrast to base substitution mutations where the mutation often has no consequence to the gene function or has only a partial effect on the gene function, a frameshift mutation completely changes the amino acid sequence downstream of the mutation site within a proteincoding gene. Thus, frameshift mutation is a severe type of mutation, which results in inactivation of the protein product most of the time. 

Silent Mutation. A base substitution that does not change the amino acid of the protein-coding gene. 

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