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Lecture 17: DNA Mutations and Damage, Point Mutations, Causes of Mutations…

- - - - one portion of chrom goes to another part of another chromosome, and vice versa
      - chronic myeloid leukemia
    - - one part of a chromosome gets inserted into another chrom
      - "fauci" anemia can cause insertion
    - - when the same region on a chromosome appears twice; gets repeated
      - fruit flies eyes
    - - chunk of chrom gets deleted and not replaced
      - cri du chat
    - - chunk of chromosome gets flipped upside down, but is read the same way so it has reverse sequence
      - blindness from acute leukemia
  - - - DNA replication
        
        DNA polymerase "slip"
        
        stalls, dissociates from strand; reanneals strands incorrectly
        
        repeat nucleotides; can lead to Huntington's
        
        End of 5' daughter strand doesn't have more nt's added (DNA pol only adds to 3' OH)
      - Formation of ribosome
    - - from ETC
      - Reactive Oxidative Species
      - electrons "leaking" back into matrix
      - super oxidizing molecules
      - Guanine: gets oxidized by ROS, gets read as Thymine
    - - base's isomer gets read as a different base because its stx is similar
        
        Thymine: usually Keto, rarely Enol
        
        Can get paired with wrong complementary base
    - - Depurinate
        
        detaches purine
        
        DNA pol adds RANDOM base
        
        attacks glycosidic linkage
      - Deaminate
        
        removal of an amino group
        
        cytosine gets read as uracil
        
        bonds btwn bases could weaken
  - - - early stop codon
      - non functional/inefficient protein
    - - insertion or deletion of 1-2 nt's; if 3 it just adds another codon
        
        AGC TTG GAC
        
        AGT CTT GGA C...
  - - - metabolism
      - radiation
      - chemicals (diet, working in ochem lab, smoking/vaping, pollution)
      - over exercising
      - respiration
      - inflammation
      - phagocytosis
    - - Non-Ionizing
        
        UV rays
        
        h-bonds btwn base pairs are split; adjacent pyrimidines form intx
        
        mutation causes thymine to absorb energy from UV radiation
        
        causes Xeroderma pigmentosa (skin cancer)
      - Ionizing
        
        x-rays
        
        cuts backbone & destroy bonds, splits helix
- - - - strand w/ incorrect BP creates mutated daughter strand
        
        all daughter strands after that will be mutated as well
        
        ONLY TAKES 1 REP to get MUT Helix
  - - - daughter strand gets mutated IN replication
        
        MUT daughter strand creates ENTIRE MUT strand
        
        one WT helix, one MUT helix
        
        takes 2 ROUNDS REP to get MUT helix
- - - - stops the rest of strand from being replicated
        
        only bad if it cuts off too many codons = non-fxl protein
- - - - transversions/transitions
      - 1/10^9 rate of error
        
        rare bc of PROOFREADING and EXONUCLEASE activity
    - - caused by: CA repeats
      - DNA pol pauses/stalls
      - daughter strand dissociates
      - daughter re-anneals incorrectly, forms "loop"
      - DNA pol adds extra nt's
      - associated with neurological damage (HUNTINGTON's)
    - - once primer is removed, DNA pol can't attach to 3'OH group
        
        creates overhanging 5' end of parent
        
        exonuclease degrades 5' end of parent strand
        
        shortens helix(telomere) every round of REP, can lead to non-fxl proteins
        
        REPAIR MECHANISM
        
        telomere: protects coding DNA from end of replication problem/exonucleases
        
        stem cells & cancer cells have telomerase turned on
        
        Telomerase: enzyme made of protein and RNA primer
        
        Primer part binds to PARENT
        
        reads its own RNA primer, adds complementary bases to PARENT 5' -> 3'
        
        After it finishes, Telomerase dissociates
        
        RNA primase adds primer
        
        DNA pol adds nt's to DAUGHTER at 3'end
  - - - ROS oxidizes molecules around it
        
        can cause mutations in DNA if it comes in contact.