DNA Replication

Question 1

dna replication is?

Answer 1

semiconservative.

Question 2

for eukaryotes, dna replication occurs during?

Answer 2

the s phase of the cell cycle.

Question 3

organization of the genome: pro vs euk chromosomes?

Answer 3

prokaryotes have one circular chromosome.
eukaryotes have several linear chromosomes.

Question 4

where does replication begin?

Answer 4

replication begins at specific sites along the dna called ORIGIN OF REPLICATION.

Question 5

what direction does replication occur?

Answer 5

bidirectionally.

Question 6

pro vs euk origin of replication?

Answer 6

prokaryotes: one origin of replication.
eukaryotes: multiple origins of replication.

Question 7

proteins that recognize the ori…?

Answer 7

bind to the dna and start to unwind it forming a replication bubble.

Question 8

what is at the end of each replication bubble?

Answer 8

the replication fork.

Question 9

what is a helicase?

Answer 9

helicase protein binds at the replication fork unwinding the dna strands. the helicase moves down the dna as replication continues.

Question 10

single stranded dna binding proteins?

Answer 10

these proteins bind to the single stranded dna and keep the strands separated.

Question 11

topoisomerases?

Answer 11

bind to the dna and helps to relieve the torsional stress.

Question 12

what does the dna polymerase do?

Answer 12

catalyze dna synthesis.

Question 13

dna polymerase iii?

Answer 13

primary enzyme of replication at the replication fork in e.coli.

Question 14

all dna polymerases synthesize dna in which direction?

Answer 14

5’ to 3’ direction.

Question 15

what does dna polymerase require?

Answer 15

a free 3’ OH group.

Question 16

how does dna polymerase make/elongate a new strand?

Answer 16

dna polymerase catalyzes the formation of a phosphodiester bond between the 3’ OH group of the growing chain and the first phosphate of the incoming nucleotide.

Question 17

dna polymerases uses what as a substrate?

Answer 17

deoxynucloetide triphosphate: dNTPS

Question 18

3 things are needed in order for dna polymerase to synthesize a complementary strand of dna?

Answer 18

1. a template that will direct the synthesis of a complementary strand of dna
2. a primer to provide a free 3’ OH group to which nucleotides can be added on to.
3. dNTPS

Question 19

dna polymerase needs something to add nucleotides on to?

Answer 19

makes use of the primer.

Question 20

what is the primer?

Answer 20

the primer is a short piece of rna that is made by an enzyme called the primase.

Question 21

what is the leading strand?

Answer 21

as chains are elongating, one is being replicated in a continuous manner. ONE PRIMING EVENT.

Question 22

what is the lagging strand?

Answer 22

the chain that is being replicated in a discontinuous manner is called the lagging strand. MULTIPLE PRIMING EVENTS.

Question 23

the segments of DNA that make up the lagging strand are called?

Answer 23

okazaki fragments.

Question 24

what about the rna primer in the lagging strand?

Answer 24

it is removed by a different dna polymerase: dna polymerase i. it replaces them with deoxynucleotides.

Question 25

what about the gaps between the okazaki fragments?

Answer 25

the gaps are sealed by an enzyme called dna ligase. the result is one continuous piece of dna.