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DNA Repair Mechanisms definitions

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  • DNA Polymerase
    An enzyme responsible for building new DNA strands and correcting errors during replication through proofreading.
  • Proofreading
    A self-correcting process where errors in newly synthesized DNA are detected and removed by a backward exonuclease activity.
  • Mismatch Repair
    A mechanism that removes and resynthesizes DNA segments containing mismatched nucleotides missed by proofreading.
  • Methylation
    A chemical modification marking the template DNA strand, allowing repair enzymes to distinguish old from new DNA.
  • Exonuclease Activity
    The removal of nucleotides from the end of a DNA strand, enabling correction of replication errors.
  • Base Excision Repair
    A pathway that removes chemically damaged nitrogenous bases and replaces them with correct ones using glycosylases.
  • Glycosylase
    An enzyme that recognizes and excises damaged nitrogenous bases, initiating base excision repair.
  • Nucleotide Excision Repair
    A process that removes bulky DNA lesions, such as thymine dimers, by excising a DNA segment and resynthesizing it.
  • Thymine Dimer
    A covalent linkage between adjacent thymine bases, often caused by UV light, that distorts DNA structure.
  • Photoreactivation
    A light-dependent repair mechanism where photolyase breaks covalent bonds in thymine dimers, restoring normal DNA.
  • Photolyase
    A light-activated enzyme that binds to thymine dimers and cleaves their covalent bonds during photoreactivation.
  • SOS Repair System
    A last-resort, error-prone DNA repair pathway activated by extensive DNA damage, involving multiple genes and enzymes.
  • SOS Mutagenesis
    The introduction of mutations during the SOS repair process due to the error-prone DNA polymerase lacking proofreading.
  • DNA Ligase
    An enzyme that seals nicks in the DNA backbone, joining newly synthesized fragments after repair.