mutations and DNA repair part 2

Question 1

mismatch repair

Answer 1

MutS and MutL come in and repair

in eukaryotes called Msh and Mlh

Question 2

mutations in Msh or Mlh

Answer 2

found in many colorectal cancers

Question 3

base excision repair

Answer 3

DNA glycosylases remove deaminated Cs and As
AP endonuclease cleaves phosphodiester bond,
DNA polymerase adds correct nucleotide and ligase seals the nick

Question 4

nucleotide excision repair

Answer 4

excision nuclease nicks damaged section of ssDNA
DNA helicase separates
DNA polymerase and ligase fix
eukaryotes, proteins are called XPA, XPB, XPC, XPD

Question 5

inability to do excision repair leads to

Answer 5

xeroderma pigmentosum

Question 6

homologous recombination

Answer 6

double-stranded break repair
nuclease digest 5’ ends of broken strands
complementary strand from sister chromosome used as template
3’ ends extended, the rest of the strands are filled in, ligase closes gaps.
error free

Question 7

nonhomologous recombination

Answer 7

double-stranded break repair
Ku complex finds broken ends
DNA protein kinase (DNA PKcs) and artemis (endonuclease)
artemis digest any ssDNA sections,
DNA ligase IV seals the strands together.
DNA is lost

Question 8

translesion DNA polymerase

Answer 8

make errors 1 in 10 nucleotides,
fill gaps when DNA is damaged
better to fill the gap and have a point mutation than to have a deletion and frameshift.