DNA Repair Flashcards
Toxic effects of DNA damage
cell cyelce arrest transcriptional responses DNA repair apoptosis mutations disease
DNA repair pathways
direct reversal of damage base excision repair nucleotide excision repair mismatch repair double strand break repair cross-link repair
Base excision repair
most endogenous toxicant-caused DNA damage such as base damage is generated by oxygen radicals and are repaired by the base excision repair pathway
nucleotide excision repair
most environmental toxicant-causes bulky DNA damages (such as)DNA damage generated by UV and cigarette smoke excision repair pathway
mismatch repair
DNA damage generated by endogenous factors such as replication errors is repaired this way
many nucleoside-based anticancer and antiviral drugs can be activated by this pathway
double strand break repair
DNA strand breaks, especially double-strand breaks generated by environmental toxicants (like ionizing radiation) and anticancer drugs (like belomycin) are repaired via this pathway
This pathway consists of homologous recombination and nonhomologous end joining sub pathways
cross-link repair
DNA interstrand crosslinks generated by DNA crosslinking reagents, such as cisplatin and psoralen are repaired via this mechanism
DNA interstrand crosslinks are repaired by a combination of several different DNA repair pathways
Mutation
an inheritable change in the sequence of the genetic materials
Types of Mutations: Base substitutions
transition - pyrimidine to pyrimidine or purine to purine
transversion - pyrimidine to purine or purine to pyrimitde
Types of Mutations: Addition/Deletions
small (a few nucleotides) - expansion and contraction of rums of nucleotides
large (several hundred to several thousand - transposon insertions, retrovirus insertions, large repetitive sequence (ex: fragile X, hunting disease, MD)
inversions and translocations
t-cell leukemia (the most frequent chromosomal abnormality is the inversion on chromosome 14)
balanced translocation = even
philadelphia chromosome is a form of leuemia and is a translocation with chromosome 22 & either 8/9
xeroderma pigmentosum
they have a defective pol eta and therefor bypass DNA polymerase
cockayne’s syndrome
proteins CSA & CSB are required for transcription-coupled NER process, if they’re not there then you get this syndrome
fanconi anemia
FA proteins are usually involved in repair of crosslink DNA damage
bloom syndrome
they carry a RecQ like helicase activity and is involved in sister chromatid exchange
