Topic 8b - DNA Repair Mechanisms and Mutations Flashcards
A mutation resulting from exposure to a mutagen from outside the cell.
Induced Mutation
Chemicals that can be incorporated into the DNA instead of a base, usually resulting in substitution.
Base Analogs
Modifies an existing base by adding a methyl or ethyl group that changes the pairing, usually resulting in substitution.
Alkylating Agent
Mimics spontaneous deamination and similarly causes a substitution.
Deaminating Agent
Modifies an existing base and results in a substitution.
Oxidative Reaction
A mutagen that binds to bases and distorts the double helix.
Intercalating Agent
Creates an extra bond between adjacent thymine nucleotides on the same strand, resulting in a thymine dimer.
UV Light Mutation
Causes base oxidation and strand breakage on one or both of the strands.
Ionizing Radiation
When a base is modified due to exposure, resulting in mis-pairs.
Base Oxidation
Acts to immediately correct substitution mutations.
Mismatch Repair
Finds chemical modifications of the old strand that have not been applied to the new strand and removes the error region allowing transcriptional polymerase to fill the gap.
Mismatch Repair in Prokaryotes
Finds nicks in the new strand and removes the error region allowing transcriptional polymerase to fill the gap.
Mismatch Repair in Eukaryotes
Targets chemically modified nitrogenous bases to replace the nucleotide using many enzymes.
Base Excision Repair
Glycosylase, AP endonuclease, DNA Polymerase I/Beta, Ligase
Base Excision Repair Enzymes
A repair enzyme that removes damaged bases.
Glycosylase
Removes the sugar-phosphate group.
AP Endonuclease
Targets bulky damage (DNA distortions) and removes the DNA segment.
Nucleotide Excision Repair
Photolyase enzymes use blue light energy to break thymine dimers, not found in placental mammals.
Photoreactivation/Direct Repair
Targets double stranded breaks and uses sister chromatids or homologous chromosomes to align the broken strand with a template using enzymes involved in meiotic recombination.
Homologous Recombination Repair
Targets double stranded breaks and uses molecules that manage recombination but can only be done immediately after synthesis using microhomologies.
Nonhomologous End-Joining
Short sequences on the ends of DNA that share a few bases.
Microhomologies
Translesional DNA polymerase is used in areas of bulky damage to replicate strands and results in a high misincorporation rate, usually only expressed due to extreme genomic damage in prokaryotes.
Translesion Synthesis
gRNA positions the Cas9 enzyme to make a double stranded break at the desired location to utilize DNA repair mechanisms to silence or edit a gene.
CRISPR/Cas9
