DNA Replication LO

Question 1

what does semi-conservative mean?

Answer 1

Newly replicated DNA has one parental strand and one daughter strand

Question 2

what does bidirectional mean?

Answer 2

replication begins at a site of origin and simultaneously moves out in both directions from this point

Question 3

how many sites of origin do prokaryotes have?

Answer 3

1

Question 4

how many sites of origin do eukaryotes have?

Answer 4

multiple

Question 5

What is a replication fork?

Answer 5

site at which DNA synthesis is occurring

Question 6

what do origin binding proteins do?

Answer 6

recognize and bind onto origins of replication

Question 7

what types of nucleotides are origins of replication rich in?

Answer 7

A and T

Question 8

what do helicases do?

Answer 8

unwinds DNA ahead of the replication fork by breaking hydrogen bonds between strands

Question 9

what do single-strand binding proteins do?

Answer 9

bind to each single strand of DNA and hold it in single stranded conformation

Question 10

What do topoisomerases do?

Answer 10

prevent extreme supercoiling of parental helix that would result as a consequence of unwinding at replication fork

Question 11

how do topoisomerases prevent supercoiling?

Answer 11

break and rejoin DNA strands

Question 12

what is important about DNA gyrase in prokaryotes?

Answer 12

can be inhibited by quinolones in treatment of disease

Question 13

which direction does DNA synthesis proceed?

Answer 13

5’ - 3’

Question 14

how does DNA polymerase work?

Answer 14

adds deoxyribonucleotides to the 3’ hydroxyls of RNA primers and subsequently to ends of growing DNA strands

Question 15

what does a primase do?

Answer 15

catalyzes the addition of RNA primer to begin replication

Question 16

what are the 2 types of DNA polymerases in prokaryotes?

Answer 16

DNA pol I and DNA pol III

Question 17

what is the major replicative enzyme for DNA and why?

Answer 17

DNA pol III because it has a sliding clamp that keeps it attached to the DNA template

Question 18

what does DNA pol I do?

Answer 18

mediates replacement of RNA primers with DNA

Question 19

through which 3 processes does DNA pol I work?

Answer 19

a. 5’ - 3’ exonuclease activity for RNA primer removal
b. 3’ - 5’ exonuclease activity for proofreading
c. 5’ - 3’ DNA polymerase activity

Question 20

what is the function of DNA Pol III

Answer 20

it is the major replicative enzyme in DNA synthesis

Question 21

why is DNA pol III the major replicative enzyme?

Answer 21

because it has a sliding clamp which keeps it attached to the DNA over a long distance

Question 22

what are the 3 DNA polymerases in eukaryotes?

Answer 22

Pol α Pol δ and Pol ε

Question 23

what is the function of DNA pol α?

Answer 23

synthesizes the first 20 DNA nucleotides after the RNA primer

Question 24

what types of activity are located in DNA pol α? (2)

Answer 24

primase activity and DNA polymerase activity

NO PROOF READING

Question 25

which polymerase performs lagging strand synthesis in eukaryotes?

Answer 25

Pol δ

Question 26

which polymerase performs leading strand synthesis?

Answer 26

Pol ε

Question 27

what serves as the primer for DNA polymerase in cells?

Answer 27

RNA

Question 28

what enzyme places the RNA primer?

Answer 28

primase

Question 29

what is the classification of primase?

Answer 29

DNA-dependent RNA polymerase

Question 30

in relation to the replication fork, which direction does the leading strand replicate?

Answer 30

towards the replication fork

Question 31

in relation to the replication fork, which direction does the lagging strand replicate?

Answer 31

away from the replication fork

Question 32

what is the name for the short sequences of DNA located on the lagging strand of DNA replication?

Answer 32

okazaki fragments

Question 33

are okazaki fragments longer in eukaryotes or prokaryotes?

Answer 33

prokaryotes (1000-2000 bp) | eurakryotes (100-200 bp)

Question 34

how are RNA primers removed?

Answer 34

through 5'-3' exonuclease | DNA pol I in E. coli

Question 35

what does DNA Pol I require on the DNA strand to start DNA synthesis?

Answer 35

3' -OH primer (RNA)

Question 36

which enzyme joins okazaki fragments together?

Answer 36

DNA ligase

Question 37

DNA ligase joins which 2 groups together?

Answer 37

3' hydroxyl group with 5' phosphate group of 2 polynucleotide chains

Question 38

Why is fidelity of replication so high?

Answer 38

1. hydrogen bonds between bp 2. geometry of AT and CG in active site of polymerase 3. proofreading through 3'-5' exonuclease activity 4. post-replication repair process

Question 39

what is reverse transcription and what enzyme performs this process?

Answer 39

synthesis of RNA to DNA | reverse transcriptase

Question 40

what is reverse transcriptase categorized as?

Answer 40

RNA dependent DNA polymerase

Question 41

what is the genetic material in retroviruses?

Answer 41

RNA

Question 42

what enzyme in eukaryotic cells has reverse transcriptase activity?

Answer 42

telomerase

Question 43

what is the job of telomerase?

Answer 43

to restore the ends of chromosomes (telomeres) in human cancer and stem cells

Question 44

how does telomerase work?

Answer 44

uses RNA template and reverse transcriptase activity to restore telomeres

Question 45

what is the "end replication problem"?

Answer 45

leading strand can be synthesized to the very end but lagging strand cannot. This causes shortening of telomeres in cells

Question 46

what happens when telomeres become too short after many round of replication?

Answer 46

cell death

Question 47

in what types of cells is telomerase activity repressed?

Answer 47

normal somatic cells

Question 48

why is telomerase a potential target in anti-cancer drugs?

Answer 48

because telomerase is not repressed in cancer cells, telomeres continue to be restored and thus cell death never occurs