Haines-8

Haines-8 - Gene Mutation, DNA repair and Transposition...

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Unformatted text preview: Gene Mutation, DNA repair and Transposition Basics on mutations A mutation is an alteration in DNA sequence. Very important process, without the variation that arises from changes in DNA sequence, there would be no phenotypic variability, no adaptation to environmental changes and no evolution. On the downside, they lead to cell death, genetic disease and cancer. Spontaneous mutations happen naturally and randomly and are usually linked to normal biological or chemical processes in the organism. Induced mutations result from the influence of an extraneous factor, either natural or artificial. The affect of the mutation will depend on where it occurs in the genome The Luria-Delbrck fluctuation test using E. coli and lytic T1 phage demonstrated that mutations are not adaptive but occur spontaneously Adaptive hypothesis: Each independent bacteria culture would have a small, but constant, probability of producing T1 resistant phage Spontaneous hypothesis: Each independent culture would have a small, but different, probability of producing T1 resistant phage, would depend on when the spontaneous mutation arose during the culture process, early=more resistant cell, late=less resistant cells Classification of Mutations Somatic mutations occur in any cell except germ cells and are not heritable. Germ-line mutations occur in gametes and are inherited. Autosomal mutations occur within genes located on the autosomes, whereas X-linked mutations occur within genes located on the X chromosome. When a recessive autosomal mutation occurs in a somatic cell of a diploid organism, it is unlikely to result in a detectable phenotype (masked by the wild-type allele). Inherited dominant autosomal mutations will be expressed phenotypically in the first generation (could have dramatic affects early in development when there are a few number of cells)....
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This note was uploaded on 04/04/2008 for the course BIO 2204 taught by Professor Athwal/haines during the Spring '08 term at Temple.

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Haines-8 - Gene Mutation, DNA repair and Transposition...

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