10 Mutations

10 Mutations - 1 Mutations and Evolution Created by Jason...

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1 Mutations and Evolution Created by Jason Mayberry for Bio200, Evolutionary Biology University at Buffalo, Fall 2007
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2 Single Gene/Point Mutations
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3 Single Gene Mutations GATTACAGATTACAG… Original GATTACA A TTACAG… GATTACA T GATTACAG… GATTACA A ATTACAG… Deletion Additions Substitution Frameshift Mutation : Changes All codons down stream of the mutation; All Amino Acids Changed. Silent Mutation if the change does not change the amino acid produced Transitions : purine purine (i.e. A G) or pyramidine pyramidine (i.e. C T) Transversions : purine pyramidine Nonsense Mutation : when a codon which normally codes for an amino acid is changed to a “stop” codon, resulting in a premature end of translation without making a complete protein POINT MUTATIONS : change a single nucleotide pair GATTAC TACTACTACTAC AGATT ACAG… Tandem Repeat Results in extra amino acids, which may seriously alter the shape/function of a protein.
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4 Synonymous (Silent) vs. Non Synonymous Mutations Synonymous Mutations (Silent) Mutations which do not alter the amino acid structure of proteins Result from Degeneracy of the Genetic Code Many third position mutations are synonymous (silent) Non-Synonymous (Missense) Mutations Mutations which do alter the amino acid structure of proteins Notice that there are more ways to produce non-synonymous mutations than synonymous mutations
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5 Mutation Rates of Point Mutations Source of Point Mutations Errors during Replication which are not fixed by proofreading Environmental factors such as UV light, chemicals, and other mutagens. Frequency of Mutations The rate of mutations varies for different species o Different efficiencies at repairing errors due to replication or external mutagens o Different protective mechanisms such as UV absorbing pigments o Different environments o Others??? Humans: ~317 mutation/gamete The mutation rate in humans is on the “slower” side compared to other organisms. Organism Base Pairs Mutation Rate per base pair per replication Virus (T2 and T4) 1.7 x 10 5 2.4 x 10 -8 E. Coli (bacteria) 4.6 x 10 6 5.4 x 10 -10 S. Cerevisiae (yeast) 1.2 x 10 7 2.2 x 10 -10 N crassa (bread mold) 4.2 x 10 7 7.2 x 10 -10 C. elegans (Nematode worm) 8.0 x 10 7 2.3 x 10 -10 D. melanogaster (fruit fly) 1.7 x 10 8 3.4 x 10 -10 Mouse 2.7 x 10 9 1.8 x 10 -10 Human 3.2 x 10 9 5.0 x 10 -11
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6 Different Ways of Looking at the Mutation Rate There are different ways to grasp the implication of mutation rates; below are a few examples for Humans: 1.How likely is it that a single base pair will be mutated? In each gamete: (317 mutations/gamete) ÷ (3.2 x 10 9 bases/gamete) = 9.9x10 -8 mutations/nucleotide In a population of 500,000 individuals: 9.9x10 -8 x 500,000 individuals = . 05 mutations/nucleotide In a thousand years of evolution where each couple only has two children.
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10 Mutations - 1 Mutations and Evolution Created by Jason...

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