DNA Replication LO Flashcards Preview

M2M Biochemistry and molecular biology > DNA Replication LO > Flashcards

Flashcards in DNA Replication LO Deck (48):
1

what does semi-conservative mean?

Newly replicated DNA has one parental strand and one daughter strand

2

what does bidirectional mean?

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

3

how many sites of origin do prokaryotes have?

1

4

how many sites of origin do eukaryotes have?

multiple

5

What is a replication fork?

site at which DNA synthesis is occurring

6

what do origin binding proteins do?

recognize and bind onto origins of replication

7

what types of nucleotides are origins of replication rich in?

A and T

8

what do helicases do?

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

9

what do single-strand binding proteins do?

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

10

What do topoisomerases do?

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

11

how do topoisomerases prevent supercoiling?

break and rejoin DNA strands

12

what is important about DNA gyrase in prokaryotes?

can be inhibited by quinolones in treatment of disease

13

which direction does DNA synthesis proceed?

5' - 3'

14

how does DNA polymerase work?

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

15

what does a primase do?

catalyzes the addition of RNA primer to begin replication

16

what are the 2 types of DNA polymerases in prokaryotes?

DNA pol I and DNA pol III

17

what is the major replicative enzyme for DNA and why?

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

18

what does DNA pol I do?

mediates replacement of RNA primers with DNA

19

through which 3 processes does DNA pol I work?

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

20

what is the function of DNA Pol III

it is the major replicative enzyme in DNA synthesis

21

why is DNA pol III the major replicative enzyme?

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

22

what are the 3 DNA polymerases in eukaryotes?

Pol α Pol δ and Pol ε

23

what is the function of DNA pol α?

synthesizes the first 20 DNA nucleotides after the RNA primer

24

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

primase activity and DNA polymerase activity
NO PROOF READING

25

which polymerase performs lagging strand synthesis in eukaryotes?

Pol δ

26

which polymerase performs leading strand synthesis?

Pol ε

27

what serves as the primer for DNA polymerase in cells?

RNA

28

what enzyme places the RNA primer?

primase

29

what is the classification of primase?

DNA-dependent RNA polymerase

30

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

towards the replication fork

31

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

away from the replication fork

32

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

okazaki fragments

33

are okazaki fragments longer in eukaryotes or prokaryotes?

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

34

how are RNA primers removed?

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

35

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

3' -OH primer (RNA)

36

which enzyme joins okazaki fragments together?

DNA ligase

37

DNA ligase joins which 2 groups together?

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

38

Why is fidelity of replication so high?

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

39

what is reverse transcription and what enzyme performs this process?

synthesis of RNA to DNA
reverse transcriptase

40

what is reverse transcriptase categorized as?

RNA dependent DNA polymerase

41

what is the genetic material in retroviruses?

RNA

42

what enzyme in eukaryotic cells has reverse transcriptase activity?

telomerase

43

what is the job of telomerase?

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

44

how does telomerase work?

uses RNA template and reverse transcriptase activity to restore telomeres

45

what is the "end replication problem"?

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

46

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

cell death

47

in what types of cells is telomerase activity repressed?

normal somatic cells

48

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

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