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DNA Repairing - Coggle Diagram

- - - - i.Base excision repair(BER)
        
        Repair of methylated, deaminated, oxidized
        bases and AP sites.
      - ii.Nucleotide exsicion repair(NER)
        
        Repair of large adducts/distortion in the
        double helical structure of DNA
        
        NER occurs in four main steps:
        (1) DNA-damage recognition
        (2) incision on both sides of the DNA lesion and removal of the damaged DNA fragment
        (3) gap-filling DNA synthesis,
        (4) ligation of open DNA ends.
  - - - Here the broken ends are repaired using the
        information on the intact sister chromatid
        ( avalaible in G2 after chromosome duplication)or on the homologous
        chromosome.
      - Two primary model
        
        1-DSBR pathway (sometimes called the double
        Holliday junction model)
        2- The synthesis-dependent strand annealing (SDSA)
        pathway.
    - - Also known as Nonhomologous End-Joining (NHEJ) or
        direct joining:
        2.Direct joining of the broken ends.
        3.This requires proteins that recognize and bind to the
        exposed ends and bring them together for ligating.
        4.They would prefer to see some complementary nucleotides but can proceed without them, so this type of joining is also called.
        5.Errors in direct joining may be a cause of the various
        translocations that are associated with cancers.
        6.Whether HRR or NHRR is used to repair double-strand
        breaks is largely determined by the phase of cell cycle.
        7.Homologous recombination repairs DNA before the cell
        enters mitosis (M phase)
        8.It occurs during and shortly after DNA replication, in the S and G2 phases of the cell cycle, when sister chromatids are more easily available
        9.While NHRR is predominant in the G1 phase of the cell cycle, when the cell is growing but not yet ready to divide.
        10.Cyclin-dependent kinases (CDKs), which modify the activity of other proteins by adding phosphate groups to (that is, phosphorylating) them, are important regulators of homologous recombination in eukaryotes.
  - - - Recognition of bases that do not form
        normal Watson-Crick pairs.
        
        DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of bases that can arise during DNA replication and recombination, as well as repairing some forms of DNA damage. Mismatch repair is strand-specific.
- - - - initial mutation inactivates a negative cell cycle regulator
        
        next mutation over activates a positive cell cycle regulator
        
        third mutation inactivates a genome stability factor
        
        additional mutation accumulate rapidly
        
        cancer cell
  - - - Apoptosis
        
        old or damaged cells normally self-destruct
      - Mitosis
        
        Interphase (cell growth)
        
        Mitotic phase (cell division)
        
        Interphase
        
        G1 phase
        
        S phase
        
        G2 phase