DNA replication and repair Flashcards
what are the three models of DNA replication?
conservative
semi-conservative
dispersion
what does semiconservative replication entail?
each daughter strand remains paired with its
complementary parental strand
what does conservative replication entail?
after replication, both daughter strands pair up
what does dispersion replication entail?
daughter strands will have a mixture of parental and newly-synthesized DNA
what is the Meselson and Stahl semiconservative replication experiment?
Track parental and newly-synthesized DNA strands over several generations with nitrogen isotopes
-Nitrogen isotopes are incorporated into the DNA molecules via nitrogenous bases
what is the DNA synthesis reaction?
Nucleotides can only
be added to the new
strand at the 3’ OH
end (therefore, DNA synthesis occurs in the 5’-3’ direction)
what provides energy for
the formation of new
phosphodiester bond?
hydrolysis of phosphate
what are the properties of DNA polymerase?
-synthesizes the new DNA strand in the 5’-3’ direction
-can only add to the 3’ end
-travels and reads the template DNA strand in the 5’-3’ direction
-can’t synthesize a new strand de novo because it requires an RNA primer with a 3’-oh end
-Single active site that can catalyze four different reactions (incorporation of
dATP, dCTP, dGTP and dTTP)
what are the 8 replication enzymes?
helicase
primase
single strand binding protein
DNA topoisomerase/gyrase
DNA polymerase 3
DNA polymerase 1
sliding clamp
DNA ligase
what is a replisome?
molecular machine of enzymes that replicate DNA
function of helicase?
Unwinds the double helix by breaking hydrogen bonds
function of primase?
Synthesizes RNA primers for DNA polymerase
what is the function of the single strand binding protein?
stabilizes ssDNA before replication by
preventing reannealing so that the strands can serve as template
function of DNA topoisomerase?
removes super coils that form ahead of
the replication fork, relieves torque of mainly circular DNA
function of DNA polymerase 3?
synthesizes DNA by adding nucleotides to
the new DNA strand
function of DNA polymerase 1?
removes RNA primer and fills the gaps with DNA
function of the sliding clamp?
attaches DNA Pol III to DNA template,
replication is more efficient
function of DNA ligase?
joins the ends of DNA segments by forming
phosphodiester bonds
