ucsdchpt18mutations

ucsdchpt18mutations - Mutations Heritable changes in the...

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Unformatted text preview: Mutations Heritable changes in the nucleotide sequence or chromosome Mutations may be: Spontaneous as a result of errors in DNA replication or Induced by exposure to radiation, chemicals, viruses, or other mutagenic agents Somatic vs Germ-line mutations Somatic Mutations occur in non-reproductive cells Mutations are not generally passed on to offspring Somatic vs Germ-line mutations Somatic Mitosis of somatic cells will pass on mutation to daughter cells Since only some cells are affected, phenotype may be minor Spontaneous Mutation Rates Studies suggest that mutations are rare 1/1,000,000 copies of a human gene Impact on the population of mutation is less severe because Nature of genetic code Recessive mutations are not expressed in the heterozygotes Lower reproductive success or early death associated with many mutations Somatic vs Germ-line mutations Somatic If mutated cells have a selective advantage, they may increase in number: Cancer Somatic vs Germ-line mutations Germ-line Mutations occur in reproductive cells Mutations may be passed onto progeny If mutation affects one homologous chromosome, expect approx 1/2 offspring to inherit the mutation Somatic vs Germ-line mutations Germ-line Progeny who inherit mutations will have mutation in ALL cells (somatic and germ-line) Mutations Two General Categories affect chromosomes mutations (Chpt 9) Mutations Two General Categories change nucleotide sequence (relatively small region) Types of Gene Mutations Base Substitutions: Point mutation: Substitution of one base for another Will result in change of one codon May affect one amino acid change Base Substitutions:Two Classes Base Substitutions:Two Classes Types of Gene Mutations Insertions and Deletions: Removal or addition of nucleotides Multiples of 3 will be in-frame insertions or deletions Types of Gene Mutations Insertions and Deletions: Removal or addition of other combinations will lead to frameshift mutations and potentially will affect many amino acids Insertion or deletion of nucleotides Reading frame is altered THE FAT CAT ATE HIS HAT Insert A THE FAA TCA TAT EHI SHA T Delete A THE FTC ATA THE ISH AT Frameshift Mutations Insertions Change the Reading Frame Fig. 11.11 Trinucleotide Repeats Class of mutations associated with a number of genetic disorders Caused by an expansion of nucleotide triplets Process is allelic expansion when the gene size is increased by an increase in trinucleotide repeats Fragile-X Syndrome...
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This note was uploaded on 01/04/2010 for the course BICD BICD100 taught by Professor Smith during the Fall '09 term at UCSD.

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ucsdchpt18mutations - Mutations Heritable changes in the...

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