lecture_24_notes

lecture_24_notes - Lecture 24 Mutation Mutations occur by...

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Lecture 24 Mutation Mutations occur by random errors during replication or because a base is damaged by a physi- cal (UV radiation) or chemical agent (more later) A mutation can entail a base substitution a base deletion or insertion Effect of mutation Silent = no effect change does not result in alterations in polypeptide ..... (some sequence). .ATGGATTTTTTGGATCCCTGA. ... DNA sequence ..... (some sequence). .ATGGA c TTTTTGGATCCCTGA. ... T->c change ATG GAc TTT TTG GAT CCC TGA codons in DNA code Met Asp Phe Leu Asp Pro stop amino acids, no change Missense = change in codon > change in one amino acid in the polypeptide ..... (some sequence). .ATGGATTTTTTGGATCCCTGA. ... DNA sequence ..... (some sequence). .ATG c ATTTTTTGGATCCCTGA. ... G->c change ATG cAU TTT TTG GAT CCC TGA codons in DNA code Met His Phe Leu Asp Pro stop amino acids, Asp>His Nonsense = change from regular codon to stop codon ..... (some sequence). .ATGGATTTTTTGGATCCCTGA. ... DNA sequence ..... (some sequence). .ATGGATTTTTaGGATCCCTGA. ... T->c change ATG GAT TTT TaG GAT CCC TGA codons in DNA code Met Asp Phe stop truncated polypeptide Frameshift = change disrupts reading frame ..... (some sequence). .ATGGATTTTTTGGATCCCTGA. ... DNA sequence ..... (some sequence). .ATGGgATTTTTTGGATCCCTGA. ... g inserted at +5 pos ATG GgA TTT TTT GGA TCC CTG A new codons in DNA code Met Gly Phe Phe Gly Ser Leu new amino acids ORF usually hundreds of codon long. A frameshift mutation alters the reading frame and usually results in the accidental formation of a stop codon in the new frame. In practice, most frameshift mutations result in shorter proteins Genes are found in genomes and are defined by the presence of a promoter, an ORF and a
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lecture_24_notes - Lecture 24 Mutation Mutations occur by...

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