lecture_19

lecture_19 - deletions or duplications of DNA between the...

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MUTATION Outline DNA replication errors Transitions and transversions Wobble errors during replications Deamination of bases Indels and replication slippage, trinucleotide diseases Radiation DNA damage and its repair
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Mutation = heritable change MOLECULAR NATURE OF MUTATION DNA Replication Errors Tautomeric shift The bases are present in the KETO form in DNA. Rare ENOL or IMINO tautomers mispair.
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Transitions Substitution: purine for purine pyrimidine for pyrimidine Transversions Substitutions: purine for pyrimidine pyrimidine for purine
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Wobble pairing during replication Deamination Frame-shift mutation: Indels addition and substitution of nucleotide Spontaneous looping of a strand during replication Replication slippage: a form of looping Isodirectional repeats occasionally SLIP during replication The process results in
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Unformatted text preview: deletions or duplications of DNA between the repeats. Trinucleotide diseases Fragile X syndrome Mental impairment 1/1500 males and 1/2500 females (CGG)n in front of FMR-1 gene Huntington disease Expansion of a repeat within the coding sequence Radiation X-RAYS: Ionization generates organic radicals. result: DNA damage, mostly breaks of DNA backbone. UV RADIATION: photoproducts crosslink adjacent pyrimidines T-A T-A cyclobutane-pyrimidine crosslink Result: insertion of anomalous bases across T-T crosslinks by SOS pathway (see later). EXCISION - REPAIR PATHWAYS GENERAL EXCISION REPAIR: E. coli uvrABC endonuclease: (1) recognition of distortions of double helix, (2) nick on each side, (3) and excision of 12-13 nucleotides. DNA polymerase I: repair DNA synthesis. LIGASE: sealing the diester bond ....
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This note was uploaded on 12/13/2009 for the course BIS 101 taught by Professor Simonchan during the Fall '08 term at UC Davis.

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lecture_19 - deletions or duplications of DNA between the...

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