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Unformatted text preview: 11-10-08 Mutations, mutagenesis and carcinogenesis I. How do different alleles arise a. Mutations: heritable changes in genes i. Allele- form of a gene; specific site on DNA ii. Occur in DNA iii. But they effect proteins iv. Point mutations 1. Structural genes a. Silent b. Mis-sense c. Nonsense d. Frameshift e. Intron/exon boundaries 2. Control genes a. Promoter/enhancer sequences b. Transcription factors b. Silent Mutations i. Mutation at position 12 in DNA: A instead of C 1. No result in amino acid sequence c. MIssense i. A base change that gives a codon for a different amino acid is a mis-sense mutation. ii. Amino acid change at position 5 bal instead of asp d. Nonsense mutation i. Mutation that makes the protein chain stop ii. Type of point mutation e. Frame-shift mutation i. Addition or deletion of a base (or 2 bases) produces a frame shift mutation f. Oxidation of guatinine i. Most common mutatino g. All cells can remove damaged bases i. repair processes h. Transparon i. Jumping gene 1. Inverted repeat 2. Proton coding gene 3. Can cause mutations by insertion II. Carcinogens a. Cancers associated with inactivation of genes b. First evidence that DNA damage indueces cancer came from study of uv radiation and skin cancer c. Sunlight induced cancer results from the inactivation of more than one gene i. P53 gene error ii. No longer have apoptosis d. IS the genetic code random? i. Crick a frozen accident ii. Evidence code is universal no selective value iii. Not frozen iv. Some variation v. The grouping of codes for hydrophobic and hydrophilic amino acids minimizes change ...
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