LEC21 - Mutation change in DNA sequence Positive Provide...

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Mutation: change in DNA sequence Positive: Provide genetic variation drive evolution Negative: lead to heritable genetic disorders in germs cells; lead to aging, cancer or neurodegenerative disorders in somatic cells Genetic tool: used to characterize genes involved in cellular processes
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Mutations in coding regions can be classified into four different groups:
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Spontaneous Mutations Replication errors Insertion of incorrect base Slippage (in reiterated sequences) Deamination of C or A Depurination (hydrolysis of G or A) Large scale rearrangements
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If replication errors are not corrected, they become permanent mutations. mutation mismatch
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Slippage during replication Repetitive sequences Slippage can cause increase or decrease in number of repeats Triplet repeats in humans neurodegenerate diseases muscular dystrophy fragile X syndrome Huntington’s disease are caused by expansion of triplet repeats Variability in dog breeds Genome has more repetitive DNA in genes Selective breeding
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Deamination of cytosine generates uracil (GCGU) depurination leaves an abasic site However, deamination of 5-mC generates T, a natural base in DNA (not repaired as often)
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Large scale mutations Not repairable Some caused by insertion of transposable elements Others include large deletions or rearrangements of chromosomes
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Mutagen Any chemical agent that causes an increase in the rate of mutation above the spontaneous level
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