L6 DNA Repair Flashcards
What damages DNA
thermal degradation, metabolic byproducts, environmental substances, radiation
What DNA vulnerable to
oxidative damage, hydrolytic attack, photolytic conversion
What does failure in DNA repair cause
mutation
Example of transition mutation
deamination
What mutation is more likely - transition or transversion
transition
Why is transition more likely
involves substituting a double ring for double ring
Transitions are less likely to result in what
amino acid substitution
What do frameshift mutations generate
missense proteins
Effect of UV light on DNA
induces formation of pyrimidine dimers
How is depurination resolved
BER pathway
Example of frameshift mutation
depurination
How does the BER pathway identify errors
base flipping strategy
What do pyrimidine dimers involve
excision of short patches of ssDNA
What can replicate highly damaged DNA
trans-lesional DNA polymerase
What can trans-lesional DNA polymerases cause
base substitution and single nucleotide deletion mutations
What do trans-lesional DNA polymerases lack
precision template recognition, exo-nucleolytic proof reading activity
What is very hazardous for a cell
double strand breaks
What causes double strand breaks
ionising radiation, replication errors, oxygen radicals
Why are double strand breaks so hazardous
no template strand to facilitate repair
What mechanisms exist to repair double strand breaks
homologous recombination, non-homologous end joining
What does non-homologous end joining require
function of DNA-PK and ATM proteins kinases
Human diseases from faulty DNA repair
Lynch syndrome, Cockayne syndrome, cancer,
What can faulty DNA repair cause
UV sensivity
