25Gene Mutation and DNA Repair.ppt

25Gene Mutation and DNA Repair.ppt - BIO 325 Genetics...

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BIO 325 – Genetics Lectures 24 and 25 Gene Mutation and DNA Repair
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Anyone can hold the helm when the sea is calm. Publilius Syrus
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A mutation is a heritable change in the genetic material. Chromosome mutations are changes in chromosome structure. Genome mutations are changes in chromosome number. Single-gene mutations are relatively small changes in chromosome structure that occur within a particular gene. Gene Mutation and DNA Repair
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Gene mutations are molecular changes in the DNA sequence of a gene. A gene mutation represents a permanent change in the DNA sequence. Consequences of Mutation
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Transitions involve a change from a pyrimidine to another pyrimidine (e.g., T to C) or a purine to another purine (e.g., A to G). Transversions involve a change from a pyrimidine to a purine, or vice-versa. Consequences of Mutation Point mutations change a single base within the DNA. Base substitutions involve a change from one base to another. 5 AACGC T AGATC 3 3 TTGCG A TCTAG 5 5 AACGC G AGATC 3 3 TTGCG C TCTAG 5
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Besides base substitutions, a single base pair or multiple base pairs may be deleted from the DNA . . . Consequences of Mutation 5 AACGC T AGATC 3 3 TTGCG A TCTAG 5 5 AACGCAGATC 3 3 TTGCGTCTAG 5 5 AACGC TAG ATC 3 3 TTGCG ATC TAG 5 5 AACGCATC 3 3 TTGCGTAG 5 . . . or added to the DNA. 5 AACGCTAGATC 3 3 TTGCGATCTAG 5 5 AAC T GCTAGATC 3 3 TTG A CGATCTAG 5 5 AACGCTAGATC 3 3 TTGCGATCTAG 5 5 AAC TAC GCTAGATC 3 3 TTG ATG CGATCTAG 5
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Consequences of Mutation Mutations within the coding sequence of a structural gene may have a number of effects on the structure of the encoded polypeptide.
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Consequences of Mutation Silent mutations do not alter the amino acid sequence of the polypeptide.
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Consequences of Mutation Missense mutations change the amino acid sequence of the polypeptide.
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Consequences of Mutation Sickle-cell anemia is an example of a missense mutation in humans.
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Consequences of Mutation Nonsense mutations change a normal codon to a stop codon. Nonsense mutations in bacterial operators may inhibit the operation of downstream genes. This is called polarity.
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Consequences of Mutation Frameshift mutations involve the addition or deletion of a number of nucleotides that are not divisible by three. This produces a completely new amino acid sequence downstream of the mutation.
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Point Mutation Examples Wild Type DNA T A C T T C A A A C C G A T T Wild Type mRNA A U G A A G U U U G G C U A A Wild Type Protein Met-------Lys-------Phe---------Gly-------Stop
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Silent Mutation (Substitution Having No Effect) Wild Type DNA T A C T T C A A A C C G A T T Wild Type Protein Met-------Lys-------Phe---------Gly-------Stop
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Silent Mutation (Substitution Having No Effect) Wild Type DNA T A C T T C A A A C C G A T T Wild Type Protein Met-------Lys-------Phe---------Gly-------Stop
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This note was uploaded on 05/19/2011 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas.

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25Gene Mutation and DNA Repair.ppt - BIO 325 Genetics...

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