HMB265H1 Chapter Notes - Chapter 15: Nonsense Mutation, Stop Codon, Genetic Screen

• School: UTSG
• Department: Human Biology
• Course: HMB265H1
• Professor: Maria Papaconstantinou

Document Summary

Cell transcribes dna to mrna, translate mrna to proteins. Heritable changes that alter sequence of nucleotide pairs = mutations. Can modify any of the steps = affect phenotype. Mutations in a gene"s coding sequence may alter the gene product. Silent mutations: changes codon into mutant codon, but mutant codon specifies exactly same amino acid. Missense mutations: changes codon into mutant codon that does specify diff aa. Conservative missense: substituted aa has similar properties to normal aa = little effect on protein function. Nonconservative missense: substituted aa very different = bigger effect on protein. Nonsense mutation: change an aa-specifying codon to a premature stop codon. = makes proteins smaller than those encoded by wt genes. Mutant polypeptide missing all the aa between the premature stop codon and the c- terminus of the normal polypeptide. If protein needs those missing polypeptides to function then won"t be able to function. Frameshift mutations: have insertion or deletion of nucleotides in coding sequence.