DNA replication

Question 1

compare and contrast DNA replication in bacteria vs eukaryotes

Answer 1

bacteria:
- circular DNA, so replication happens in both directions and the ends meet up
- only one origin of replication is needed
eukaryotes:
- large and linear DNA, so multiple origins of replication are needed

Question 2

oriC

Answer 2

origin of DNA replication in bacteria

Question 3

oriR

Answer 3

origin of DNA replication in eukaryotes

Question 4

in what direction does DNA replication occur?

Answer 4

5’ to 3’

Question 5

in which direction is the DNA template read by DNA pol?

Answer 5

3’ to 5’

Question 6

NTPs

Answer 6

nucleotide triphosphates - building blocks of DNA and RNA

Question 7

compare and contrast dNTPs and rNTPs

Answer 7

dNTPs - DNA monomers (dATP, dGTP, dCTP, dTTP)
rNTPs - RNA monomers (rATP, rGTP, rCTP, rUCP)

Question 8

how does ATP hydrolysis provide energy to drive polymerization?

Answer 8

ATP hydrolysis is a catabolic reaction where one or more phosphates in ATP are released, releasing chemical energy that was stored within the bonds. this energy can be used to link monomers together

Question 9

are the bonds between phosphate groups in ATP strong or weak? why?

Answer 9

the bonds are weak b/c the phosphates are all negatively charged and repel each other (keeping them in close proximity is energetically unfavourable)

Question 10

true or false: ATP hydrolysis is spontaneous

Answer 10

true! ATP hydrolysis is energetically favourable b/c the negatively charged phosphates are further apart from each other

Question 11

DNA polymerase

Answer 11

enzyme that reads the DNA template and synthesizes new DNA by linking nucleotides together

Question 12

can DNA polymerase start replication from scratch?

Answer 12

no (lmao L). it always needs to start from the 3’ OH end of an existing template, so it requires a primer to work from

Question 13

what is the primer used by DNA pol in replication?

Answer 13

RNA primer

Question 14

semiconservative replication

Answer 14

each new DNA molecule contains one parent strand and one newly synthesized daughter strand

Question 15

activated monomers

Answer 15

triphosphates (eg. dNTPs, rNTPs) that provide energy for cellular reactions

Question 16

helicase

Answer 16

breaks hydrogen bonds b/w DNA bases, which separates the 2 strands

Question 17

primase

Answer 17

lays down RNA primers on leading and lagging strands

Question 18

DNA polymerase I

Answer 18

proofreads DNA by replacing RNA primers with DNA nucleotides

Question 19

topoisomerase

Answer 19

relaxes supercoiled DNA

Question 20

single-stranded binding proteins

Answer 20

coats single-stranded DNA to make sure the strands stay separated

Question 21

DNA polymerase III

Answer 21

synthesizes DNA 5’ to 3’ on leading and lagging strands, working from RNA primers

Question 22

DNA ligase

Answer 22

joins okazaki fragments by catalyzing the formation of phosphodiester bonds b/w adjacent nucleotides

Question 23

why does DNA replication involve leading and lagging strands?

Answer 23

DNA replication always occurs 5’ to 3’. since one template strand is 3’ to 5’ away from the replication fork while the other is 5’ to 3’ away from the replication fork, replication of one strand can occur continuously while the other occurs in fragments

Question 24

okazaki fragments

Answer 24

sections of DNA between primers

Question 25

which strand has more RNA primers?

Answer 25

lagging strand

Question 26

how is the lagging strand different from the leading strand?

Answer 26

- the lagging strand is synthesized in the direction opposite to the direction of the replication fork - the lagging strand needs many RNA primers

Question 27

compare and contrast DNA pol III and DNA pol I

Answer 27

both elongate DNA by adding nucleotides to a 3' OH, but DNA pol III carries out the bulk of replication while DNA pol I proofreads by replacing RNA primers with DNA

Question 28

continuous vs discontinuous synthesis

Answer 28

continuous synthesis - replication occurs continuously on the leading strand discontinuous synthesis - replication occurs in fragments on the lagging strand

Question 29

during which stages of bacterial population growth does DNA replication occur?

Answer 29

lag phase to stationary phase