CH7-2 - Xeroderma pigmentosum Mutation in one of seven...

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Chapter 7 Part II DNA repair mechanisms Exam 2 next Tuesday (chapters 5, 6, 8, 7)
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DNA repair mechanisms Enzymes Photolyase Simple repair systems Base excision repair Nucleotide excision repair Error-prone repair systems SOS system Nonhomologous end-joining Simple/routine Complex/ last resort
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Photolyase Breaks thymine dimers (from UV radiation)
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Base excision repair Deaminated DNA with uracil Glycosylase removes uracil Endonuclease cuts backbone Exonuclease removes nucleotides near the nick DNA Polymerase makes new DNA to fill the gap Ligase seals the nick
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Nucleotide excision repair
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SOS system Involves “sloppy” DNA polymerases Detects stalled DNA replication Add random nucleotides across from the damaged bases
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Non-homologous end-joining Results in deletions!
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Mutations in genes encoding DNA repair proteins affect human health
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Unformatted text preview: Xeroderma pigmentosum Mutation in one of seven genes for a DNA repair mechanism. Which one? Clicker: A defect in which repair mechanism likely leads to Xeroderma pigmentosum? 1. Base excision repair 2. Nucleotide excision repair 3. SOS system 4. Nonhomologous end-joining The Ames test A test for carcinogens using his-mutants of Salmonella typhimurium Genes encode polypeptides • Proteins are made of polypeptides (1 or more) • Monomer = Amino acid: Amino (-NH 2 ) group CHR group Carboxyl (-COOH) group Peptide bonds are formed via: Dehydration reactions Protein structure Quarternary structure: more than one polypeptide How do genotypes and phenotypes correlate? Different amino acid substitutions lead to different phenotypes...
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CH7-2 - Xeroderma pigmentosum Mutation in one of seven...

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