Unit 4: DNA Repair Flashcards
What is a point mutation?
change in single base pair
What is a transition?
Interchange of purine to purine or pyrimidine to pyrimidine
What is a transversion?
Interchange of purine for pyrimidine or vice versa
What causes a small indel?
Replication slippage, or repair of a DNA double strand break
What is a frameshift mutation?
When a nucleotide insertion or deletion is a multiple of 1 or 2
What are the large-scale mutations?
Deletion, Duplication, or Inversion
What is the cause and consequence of DNA cross-links?
Cause: UV irradiation
Consequence: Replication for stall, risk of DNA break
What is the cause and consequence of DNA breaks?
Cause: ionizing radiation
Consequence: broken DNA, large chromosomal rearrangements
What are the steps of Base excision repair?
- Damage bases recognized and removed by Glycosylase
- AP endonuclease cleaves DNA upstream of abasic site
- Polymerization or removal of lyase
- Ligation
What are the steps of nucleotide excision repair?
- Recognition of the lesion
- Nicks around the lesion
- Excision, replication, ligation
What are the steps of mismatch repair?
- Mismatch recognized by specific proteins
- Newly synthesized strand is hemimethylated
- scans DNA for DMA1 sites, forming a loop, and recruits repair molecules
- Helicase II and Pol I exonuclease unwind and degrade the newly replicated DNA strand past the mismatch
What is non-homologus end joining?
No homology required Minor-end processing Very efficient but can be toxic Active whole interphase Dominant
What is homologous recombination?
Sister chromatid required
Active only during S and G2 phase
Very accurate
What are the 2 main uses of CRISPR/Cas9?
Using NHEJ to cause gene disruption or using HR for gene edition
