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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
– 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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