ch 4 Flashcards
define parent strands of DNA
old strands of DNA
define daughter strands of DNA
new strands of DNA
where are DNA strands separated at for DNA replications
replication fork
where does DNA replication begin
origins of replication
define ORC proteins
“origin recognition complex”
binds to origin of replication to begin DNA replication
define helicase
protein that unwinds DNA
define single-stranded binding proteins
proteins that binds to DNA and keeps two strands separate
define topoisomerases
enzymes that relieve the stress on DNA strands
1.) cut DNA
2.) allows strand twisting
3.) they re-ligate DNA
define DNA polymerases
enzyme that adds nucleotides to growing DNA chain
1.) reads parent strand
2.) adds complementary nucleotides in order
3.) makes daughter strand
define sliding clamp
keeps DNA polymerase from falling off DNA
what direction does DNA polymerase add nucleotides in
5’ to 3’
define leading strand
daughter strand that goes in the same direction as replication fork
define lagging strand
daughter strand that does in the opposite direction as replication fork
define okazaki fragments
disconnected DNA fragments on lagging strand
define primase
enzyme that primes RNA sequence for DNA replication
define exonuclease
enzyme that removes incorrectly placed nucleotides and the primer region
define DNA ligase
enzyme that joins the Okazaki fragments together
define telomerase
adds telomeres to the end of chromosomes
types of DNA damage
double-strand break
incorrect nucleotide pairing
damage base
intra-strand crosslink
define deamination
cytosine breaking into uracil
define photoreactivation
repair process that fixes damaged pyrimidine dimers
photolyase
light activated repair enzyme involved in photoreactivation
what happens in base-excision repair
defective base is removed and replaced by enzymes
define abasic site
sugar phosphate backbone but no base
define nucleotide-excision repair
entire nucleotides are removed
helicase recognizes damage
define excinuclease
enzyme that excises the DNA in nucleotide
define translesion synthesis
specialized DNA polymerase that moves past DNA mutation
define nonhomologous end joining
DNA ligase repairs ends
define homology directed repair
undamaged chromosome is used as repair template
