DNA Repair and Replication Flashcards
what are the 3 fundamental condition of DNA replication?
semiconservative, bidirectional, semi discontinuous
in the semi conservative method, one strand of the newly synthesized strand is ____ to the original
complementary (A-T, C-G)
what is the name of the site of origin in unidirectional replication?
Ori-C
okazaki fragments are liked via ____ bonds
covalent
in what direction is the leading strand synthesized?
5’ to 3’
what enzyme synthesizes DNA?
DNA polymerase
____ ____ is the enzyme that links together okazaki fragments
DNA ligase
what are the 3 phases of DNA replication?
initiation, elongation, termination
what is the initiation factor that binds to OriC to separate the strands of the double helix?
DnaA protein
what is the role of DnaA protein?
bind to oriC to separate the strands of the double helix
what helicase binds to the separated strands and moves alone the DNA to unwind the DNA double helix?
DnaB protein
what is the role of DnaB protein?
bind to the separated strands to unwind the double helix
what is the protein that prevents the two unwound DNA strands from coming back together?
SSB (single-stranded DNA binding protein)
what is the role of SSB (single-strand DNA binding protein)?
prevent the separated strands from coming back togehter
what protein relieves stress in the helical DNA caused by the unwinding?
DNA gyrase (DNA topoisomerase 2)
____ copies of the DnaA protein bind to oriC
multiple
what two proteins are responsible for bringing in the DnaB protein?
DnaC and DnaT
DnaB subunits come in the form of a ____
hexomere
DnaB subunits come in the form of a ____
hexamer
SSB subunits come in the form of _____
tetromers
SSB subunits come in the form of _____
tetramers
what are the two enzymes responsible for DNA unwinding during the elongation phase?
DNA helicase (DnaB), gyrase (topoisomerase 2)
what enzyme is responsible for synthesizing an RNA primer that is needed for DNA replication in the elongation phase?
primase
what enzyme is used in the elongation phase to synthesize the new DNA strands?
DNA polymerase 3 holoenzyme
what subunit of DNA polymerase 3 acts as a “sliding clamp” that hold the DNA polymerase onto the DNA strand?
beta
what second enzyme is associated with DNA polymerase 1?
DNA ligase
what enzyme during elongation is responsible for binding to the region of the primers that will begin the Okazaki fragment to cut it out and replace it with a patch of DNA?
DNA polymerase 1
how many subunits are a part of DNA polymerase 3 holoenzyme?
10
what part of DNA polymerase 3 holoenzyme is involved in polymerase activity of linking new nucleotides to the end of the growing chain via covalent linkages?
alpha
what part of DNA polymerase 3 holoenzyme has 3’ to 5’ proofreading activity?
episilon
what part of DNA polymerase 3 holoenzyme stimulates the proofreading activity?
theta (O)
in DNA polymerase 3 holoenzyme, how many core units of A,E,T are present?
2
what is the middle core of DNA polymerase 3 holoenzyme?
gamma
what complex keeps together the 2 A,E,T cores?
gamma complex
what are the components of the gamma complex?
gamma, delta, delta prime, chi, si
how many tau and beta are present at each A,E,T core?
1 tau, 2 beta
what is the role of tau in DNA polymerase 3 holoenzyme?
to bring about proper assembly
at termination, what is the name of the termination region?
ter
what is the termination protein that is bound to the termination region (ter) to help bring about termination?
tus
DNA in higher cells interact with ____ proteins to form ______ and ______ ______
histones, nucleosomes, chromatin fibers
are histones positively or negatively charged?
positively charged to bind to the negatively charged DNA
what occurs to disrupt the positive charges on the histones so they fall off?
acetylation (binding of acetyl group to neutralize)
how many DNA polymerases are needed in eukaryotic DNA replication?
5
what eukaryotic DNA polymerase functions in the initiation of nuclear DNA replication by initiating the addition of DNA nucleotides to the end of the primer?
alpha
what eukaryotic DNA polymerase is the principle DNA polymerase in replication, and grows the okazaki fragments?
delta
what eukaryotic DNA polymerase cooperates with delta to produce the leading strand?
epsilon
what eukaryotic DNA polymerase functions in DNA repair?
beta
what eukaryotic DNA polymerase is the DNA replicating enzyme of the mitochondria
gamma
polymerase ___ has 4 subunits with 2 involved in DNA replication and 2 involved in primase (RNA) synthesis
alpha
what eukaryotic DNA polymerase has the 4 subunits of PolA1, PolA2, Prim1, and Prim2?
alpha
what eukaryotic DNA polymerase has the 5 subunits of PolyD1, PolyD2, PolyD3, PolyD4, and PCNA (clamp)?
delta
what eukaryotic DNA polymerase has the 3 subunits of Pole, Pole2, and Pole3?
epsilon
what eukaryotic DNA polymerase has the 2 subunits of PolG and PolG2?
gamma
what eukaryotic DNA polymerase has low fidelity?
beta
what eukaryotic DNA polymerases have low processivity?
alpha, beta
what is the eukaryotic protein that bind to to the replication origins and is important to bringing about the assembly of the pre-replicative complex?
ORC
what is the eukaryotic protein that acts as a helicase to unwind the double helix at replication origins and separate DNA strands?
MCM (replaces DnaA and DnaB)
what is the eukaryotic protein that brings about the binding of the MCM proteins to the replication origins?
Cdc6 (no active role)
what is the eukaryotic protein that is a kinase complex that initiates DNA replication by adding phosphate groups to ORC, MCM, and Cdc6 proteins?
cyclin CDK (negative charged phosphate changes protein folding and activates them)
in eukaryotes, a pre-replication complex is formed by the binding of ____ and ____ proteins to the replication origin where ____ protein is bound
Cdc6, MCM, ORC
ORC is duplicated during the ___ phase
S
a gap is produced at the ___ end by the removal of the RNA primer
5’
_____ is the enzyme responsible for extending the 3’ end in eukaryotes by adding TTAGGG repeats so that DNA polymerase can extend the 5’ end
telomerase
telomerase adds sequences of ______ bases
TTAGGG
____ ____ occur when pyrimidine bases such as T are covalently linked by UV light
pyrimidine dimers
___ ___ ____ is when DNA corrects errors introduced when DNA is replicated
mismatch repair system
___ ___ _____ acts on single bases damaged by oxidation or other chemical modifications
base excision repair
_____ ____ ____ repairs large regions of damaged DNA
nucleotide excision repair
______ ___-_______ is correcting DNA double strand breaks caused by radiation or when free radicals are repaired
nonhomologous end-joining
___ _____ uses homologous recombination to repair double strand breaks that occur ding cell division cycle
recombination repair
__ ____ ___ _____ are when chemically modified bases are directly repaired
direct reversal repair systems
photolyase, an enzyme that repairs thymine dimers, is an example of what repair mechanism?
direct reversal repair systems
to ID the strand with the incorrect base in mismatch repairs, ____ groups are detected as only being on the old strand
methyl
the strand ____ the methyl groups in mismatch repair is the new strand
without
what 3 enzymes are needed during mismatch repair to remove the incorrect nucleotide and replace it?
endonuclease, exonuclease, DNA polymerase 3, DNA ligase
in base excision repair, ___ ____ removes the damaged based by cleaving the glycosidic bone between the base and deoxyribose
DNA glycosylase
in base excision repair, an _____ cleaves the backbone to remove the deoxyribose and phosphate group
endonuclease
in base excision repair, an _______ removes a number of additional nucleotide residues that are not damaged to create space for DNA polymerase 1 to come in and add a patch of DNA
exonuclease
an ____ site is created in base excision repair after cleavage
AP (apurinic, apyrimidinic)
in base excision repair, ___ _____ ____ fills in the made gap with a patch of DNA
DNA polymerase 1