DNA replication and repair

Question 1

what are the three models of DNA replication?

Answer 1

conservative
semi-conservative
dispersion

Question 2

what does semiconservative replication entail?

Answer 2

each daughter strand remains paired with its
complementary parental strand

Question 3

what does conservative replication entail?

Answer 3

after replication, both daughter strands pair up

Question 4

what does dispersion replication entail?

Answer 4

daughter strands will have a mixture of parental and newly-synthesized DNA

Question 5

what is the Meselson and Stahl semiconservative replication experiment?

Answer 5

Track parental and newly-synthesized DNA strands over several generations with nitrogen isotopes
-Nitrogen isotopes are incorporated into the DNA molecules via nitrogenous bases

Question 6

what is the DNA synthesis reaction?

Answer 6

Nucleotides can only
be added to the new
strand at the 3’ OH
end (therefore, DNA synthesis occurs in the 5’-3’ direction)

Question 7

what provides energy for
the formation of new
phosphodiester bond?

Answer 7

hydrolysis of phosphate

Question 8

what are the properties of DNA polymerase?

Answer 8

-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)

Question 9

what are the 8 replication enzymes?

Answer 9

helicase
primase
single strand binding protein
DNA topoisomerase/gyrase
DNA polymerase 3
DNA polymerase 1
sliding clamp
DNA ligase

Question 10

what is a replisome?

Answer 10

molecular machine of enzymes that replicate DNA

Question 11

function of helicase?

Answer 11

Unwinds the double helix by breaking hydrogen bonds

Question 12

function of primase?

Answer 12

Synthesizes RNA primers for DNA polymerase

Question 13

what is the function of the single strand binding protein?

Answer 13

stabilizes ssDNA before replication by
preventing reannealing so that the strands can serve as template

Question 14

function of DNA topoisomerase?

Answer 14

removes super coils that form ahead of
the replication fork, relieves torque of mainly circular DNA

Question 15

function of DNA polymerase 3?

Answer 15

synthesizes DNA by adding nucleotides to
the new DNA strand

Question 16

function of DNA polymerase 1?

Answer 16

removes RNA primer and fills the gaps with DNA

Question 17

function of the sliding clamp?

Answer 17

attaches DNA Pol III to DNA template,
replication is more efficient

Question 18

function of DNA ligase?

Answer 18

joins the ends of DNA segments by forming
phosphodiester bonds