GEN-3020 Lecture Notes - Lecture 15: Missense Mutation, Nonsense Mutation, Silent Mutation
8 Nov 2016
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Gen 3020: chapter 15-gene mutation, dna repair, and. Mutation is an alteration in dna sequence, any base-pair change, single base pair substitution, deletion or insertion, major alteration in chromosomal structure. It may occur in somatic or germ cells as well as in coding or noncoding regions. Point mutation, or base substitution, is a change from one base pair to another. Transitions are like replaces like (pyrimidine replaces pyrimidine; purine replaces purine). May result in a new codon for a different amino acid (missense mutation), stop codon (nonsense mutation), or for the same amino acid (silent mutation). Frameshift mutations result from insertions or deletions of a base pair. Loss of function mutation reduces function of gene product. Null mutation results in complete loss of function. Dominant mutation results in mutant phenotype in diploid organisms. Dominant gain of function mutation results in gene with enhanced, negative, or new function. Lethal mutations interrupt essential processes and result in death (tay-
