Lecture.20.Fall.2013

G 2 the lac superrepressor mutation usually dominant

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Unformatted text preview: s-of-function and Gain-of-function mutations • Gain-of-function mutations • e.g. 2: The lac superrepressor mutation • Usually dominant, as the protein is now doing something it did not previously do. and causes effect Other types of mutations stops wild type protein fro funtcioning • Dominant negative: mutant protein interferes with the function of the wild type protein, leading to a dominant loss-of-function phenotype • Regulatory: disrupts the regulation of a gene’s expression (promoter or enhancers) – May be lof or gof mutations, dominant or recessive Other types of mutations • Conditional mutations: lof mutations in which the protein is functional under some conditions, but nonfunctional in others – Temperature sensitive mutations • Lethal mutations cause death, of either the cell or the organism. • Almost always recessive. Why? if mutation is lethal, progeny cannot be proopagated Suppressor mutations Suppressor mutations • Two classes of suppressor mutations: • Intragenic suppressor mutations are in the same gene as the original mutation. • May change a second nucleotide in the codon altered by the original mutation, so that it specifies the WT amino acid. • May suppress a frameshift mutation: • By inserting a nucleotide(s) after a deletion • Or deleting a nucleotide(s) after an insertion. all codon downstream become normal if 1 is added triplet code is degenerate Text Suppressor mutations Intragenic suppressor mutations • May make a compensatory change in a protein • A first missense mutation may alter the folding of a protein by destroying an interaction between amino acids. make change elsew...
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