DNA Replication (Lecture 12)

Question 1

What does it mean that DNA synthesis is semi-discontinuous?

Answer 1

lagging strand replicates discontinuously while lagging strand is continuous

Question 2

What are the 4 universal rules for DNA replication that viruses need to adhere to?

Answer 2

need DNA (3’-5’) template, need a free 3’OH end, synthesis occurs 5’-3’, replication occurs only at Ori’s, need accessory proteins such as helicase, always primer dependent

Question 3

What are the 4 obstacles that DNA viruses face when it comes to DNA synthesis?

Answer 3

DNA polymerase not always present, no telomeres on their genome but need to replicate their whole genome, replication machinery only recognizes eukaryotic DNA, at least one viral protein is used SO DNA replication is postponed until viral protein is made

Question 4

What are the 4 essential genes/proteins for DNA viruses?

Answer 4

DNA polymerase and accessory proteins, origin of binding protein and helicase, endonucleases, enzymes needed for nucleic acid metabolism (synthesis) which host cells do not have

Question 5

What do TRL and TRS stand for?

Answer 5

terminal repeats long and short

Question 6

What do IRS and IRL stand for?

Answer 6

internal repeats short and long

Question 7

What are the 2 ways that dsDNA can be replicated?

Answer 7

replication fork synthesis and strand displacement

Question 8

What is replication fork synthesis?

Answer 8

replication occurs on BOTH strands and uses RNA primer

Question 9

What is strand displacement synthesis?

Answer 9

replication only occurs on one strand while other strand is displaced, uses a DNA primer OR a protein primer (ie: serine)

Question 10

With SV40 viruses (dsDNA), what is the first biosynthetic event?

Answer 10

synthesis of LT viral protein

Question 11

What is the LT viral protein?

Answer 11

has helicase activity, recognizes Ori and binds to it

Question 12

What type of DNA replication do parvovirus undertake? What do they use as a primer?

Answer 12

continuous and DNA

Question 13

What is the viral protein that parvovirus need for DNA replication and what is its function?

Answer 13

Rep78/68, viral endonuclease

Question 14

What is the purpose of Rep78/68?

Answer 14

creates a new free 3’OH

Question 15

What is pTP?

Answer 15

viral protein used by adenoviruses as a primer

Question 16

What type of DNA replication do adenoviruses undertake?

Answer 16

strand displacement with no end problem

Question 17

What is rolling circle replication and which viruses perform this kind of method?

Answer 17

continuous DNA synthesis

Question 18

What are the 2 required to carry out the rolling circle replication?

Answer 18

endonuclease to put a nick in the DNA and DNA polymerase

Question 19

What is a concatemer? And how is it packaged into progeny virions?

Answer 19

identical genomes that are connected but will be cut into seprate genomes during packaging and will be packaged each into a new virion

Question 20

What are the 2 obstacles for DNA viruses? And the solutions (if any) to these obstacles?

Answer 20

lack of telomeres (solved with concatemers) and DNA polymerase as it is not always presemt inside the cell

Question 21

What is the protein that regulates the START checkpoint’?

Answer 21

Rb protein

Question 22

What is the start checkpoint of the cell cycle?

Answer 22

checks if the cell has grown enough with enough proteins and nutrients to undergo cell division?

Question 23

What happens once you pass the start checkpoint?

Answer 23

cell is commited to cell divison, either it will divide or undergo apoptosis

Question 24

What is the Rb protein? What is it’s role?

Answer 24

holds onto E2F and keeps it until it is phosphorylated and releases E2F

Question 25

How do viruses make DNA polymerase available?

Answer 25

viruses target Rb protein by making a viral protein that can bind to Rb so that it releases E2F

Question 26

What is E2F and what is its role?

Answer 26

a transcription factor that binds to DNA and turns on gene expression