Chapter 8

Question 1

dna replication is?

Answer 1

semi conservative

Question 2

when does dna replication occur for eukaryotes?

Answer 2

it occurs during the S phase of the cell cycle(dna synthesis)

Question 3

chromosome for prokaryotes vs eukaryotes

Answer 3

prokaryotes: one circular chromosome
eukaryotes: several linear chromosomes

Question 4

where does replication begin?

Answer 4

special sites along the dna called the ORIGIN OF REPLICATION

Question 5

replication occurs …?

Answer 5

bidirectionally

Question 6

origin of replication in prokaryotes vs eukaryotes?

Answer 6

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

Question 7

proteins recognize the “ori” aka origin of replication and then…?

Answer 7

bind to the dna and start unwinding it forming a replication bubble ( the structure that forms during dna replication when the double helix unwinds at the ori )

Question 8

what is at the end of each replication bubble?

Answer 8

the replication fork: y shaped structure that progresses as replication occurs, it moves along the dna as more of the double helix unwinds.

Question 9

what is helicase?

Answer 9

helicase is an enzyme that plays a role to unwind and separate the two strands by breaking the hydrogen bonds between the nitrogenous bases.
- binds at the replication fork

Question 10

what are other proteins involved in replication?

Answer 10

single stranded dna binding proteins: bind to single stranded dna and keep strands separated
topoisomerases: helps relieve the torisonal stress and bind to dna

Question 11

what does the enzyme dna polymerase do? give e.coli information

Answer 11

dna polymerase is an enzyme that catalyzes dna synthesis.
e coli: dna polymerase iii primary enzyme of replication at the replication fork

Question 12

what direction do dna polymerase synthesis dna in?

Answer 12

5’ to 3’ direction

Question 13

no known dna polymerase can…?

Answer 13

synthesize dna de novo

Question 14

dna polymerase requires?

Answer 14

a free 3’ -OH group

Question 15

what is the substrate that the dna polymerase uses?

Answer 15

dNTPS: deoxynucleotide triphosphate: consists of sugar, nitrogenous base, and 3 phosphate groups.

Question 16

so what happens when dntp is available?

Answer 16

it binds to the dna polymerase. the enzyme then checks the base of the incoming dntp against the base on the template strand. if the template is a it will pair with t from the dntp. etc. this allows the dna polymerase to catalyze the formation of a new phosphodiester bond.

Question 17

summary of dna polymerase/dntp?

Answer 17

dna polymerase helps ensure that the new dna strand is an accurate copy of the template by matching each incoming dntp to its complementary base on the template strand.

Question 18

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

Answer 18

• a template that directs the synthesis of complementary dna strand.
• a primer to which nucleotides can be added to.
• dntps

Question 19

what is a primer?

Answer 19

the primer is a short piece of rna that is made by enzyme called PRIMASE

Question 20

as chains are elongating, one is being replicated in a continuous manner?

Answer 20

leading strand: one priming event

Question 21

the other chain is being replicated in a discontinuous manner?

Answer 21

lagging strand: multiple priming events

Question 22

what are the segments of dna that make up the lagging strand called?

Answer 22

okazaki fragments

Question 23

what about the primer in the lagging strand?

Answer 23

it is removed by a different dna polymerase: dna polymerase i
- it is then replaced with deoxynucleotides

Question 24

what about the gaps between the okazaki fragments?

Answer 24

they are sealed by an enzyme called DNA LIGASE