Molecular Genetics: Dna Replication

Question 1

what acts as templates in DNA replication?

Answer 1

An old parent strand and a new daughter strand

Question 2

what does semi-conservative mean?

Answer 2

Each strand contains one old parent stand and one new daughter strand

Question 3

what is the replication origin?

Answer 3

where proteins bind at specific sites on the DNA and where DNA replication starts

Question 4

what is the function of helicase?

Answer 4

break the hydrogen bonds between the complementary base pairs

Question 5

what is the function of single-stranded binding proteins?

Answer 5

prevent the two DNA strands from recoiling as they have a natural desire to reanneal

Question 6

what is the function of the enzyme Gyrase or Topoisomerase?

Answer 6

works to relieve the tension of the uncoiling strands by cutting them and allowing them to swivel around one another, then reseal the strand after replication is complete

Question 7

what is the replication fork

Answer 7

when the two strands separate at the origin of replication

Question 8

how do replication bubbles form?

Answer 8

when two forks arise close together a replication bubble forms

replication proceeds towards the fork on one strand and away from the fork on the other strand.

Question 9

which direction can DNA polymerase build the complementary strand ?

Answer 9

in the 5’ to 3’ direction towards the replication fork

(because the enzyme that adds new bases to a growing strand requires a free 3’ OH group).

Question 10

where is the deoxyribonucleoside triphosphate strand added to the elongating strand?

Answer 10

to the 3’ end of the elongating strand. They use the free hydroxyl group found at the 3’ ends as a hook adding a nucleoside to this group through a polymerization reaction

Question 11

what does DNA polymerase require to begin elongation?

Answer 11

an initial 3’ starting end

Question 12

how many base pairs does DNA polymerase anneal to a template strand?

Answer 12

10-60

Question 13

what does the primer DNA Polymerase III mark the initial sequence of DNA replication as?

Answer 13

Marks the initial sequence as temporary for easy removal

Question 14

what is the function of Polymerase III?

Answer 14

add new deoxyribonucleoside triphosphates on the elongating strand and proofreading

Question 15

which DNA strand is synthesized continuously as a single strand?

Answer 15

-the leading strand

-built in the 5’ to 3’ direction can be synthesized continuously

Question 16

what are the short fragments of the lagging strand called?

Answer 16

Okazaki fragments

Question 17

what is the function of DNA polymerase I?

Answer 17

removes the RNA primers from each strand and replaces them with the appropriate nucleoside

Question 18

what is the function of DNA ligase?

Answer 18

joins the Okazaki fragments using phosphodiester bonds to form one continuous strand

Question 19

what is the common function of Polymerase I and III?

Answer 19

they proofread and act as exonuclease by cutting out incorrectly paired nucleotides and replacing them with the correct bases

Question 20

what is the result of DNA replication

Answer 20

2 identical DNA molecules, one for each daughter cell in mitosis.

Question 21

what enzyme makes the RNA primer?

Answer 21

Primase

Question 22

which enzyme adds new complementary base pairs?

Answer 22

DNA polymerase

Question 23

what carries the genetic information of an organism in DNA?

Answer 23

the sequence of nucleotides

Question 24

what is the goal of DNA replication?

Answer 24

generate two identical DNA molecules before a cell can divide