Lecture 10 Bio325 Fall 07

Lecture 10 Bio325 Fall 07 - Early experiments...

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1 Early experiments characterizing the nature of a gene relied on the effects of mutations Fig. 7.2 • the “normal” allele of a gene in a population is the wild-type allele; all other alleles are mutant alleles. However, mutant alleles by this definition may still have normal function • inversions and reciprocal translocations are just two of many types of chromosomal rearrangements Do cells respond to life-threatening situations by mutating specific genes, or do mutations happen randomly? mutations happen randomly! this is also one of the primary tenets of evolution Fig. 7.5
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How do mutations occur? natural processes: • misincorporation during DNA replication (although this rate of mutation is low due to the 3’ to 5’ exonuclease activity of cellular DNA polymerases) • oxidation by natural metabolic intermediates leading to oxidation, depurination, or deamination some changes can lead to permanent changes in DNA sequence if they are not repaired Fig. 7.6 How do mutations occur? external and unnatural sources: • radiation: UV (causes single-strand adducts which can become double-strand breaks during replication), X-rays (cause double-strand breaks directly as well as single-strand breaks, protein damage, and protein-DNA adducts) • chemical exposure: alkylating agents, intercalating compounds, base analogs. All of these modify DNA and block or stall replication example: Benzo-[a]-pyrene (one of the
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

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Lecture 10 Bio325 Fall 07 - Early experiments...

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