Rodgers 2-12 thru

Question 1

What are the main polymerases in eukaryotes?

Answer 1

Pol E for the leading strand, Pol D for the lagging strand

Question 2

What protein ties the polymerases together to synchronize replication?

Answer 2

Replication Factor C (RFC)

Question 3

What role does Proliferating Cell Nuclear Antigen play in replication

Answer 3

PCNA is the clamp that coordinates different replicative proteins to the DNA depending on their activation by Cdk’s, used as the processive helicase by all polymerases

Question 4

What is the name of eukaryotes’ version of SSB?

Answer 4

RPA (Replication Protein A)

Question 5

What happens to the unopened region of the DNA as replication occurs

Answer 5

It builds positive supercoils

Question 6

How does gyrase operate? What type of topoisomerase is it?

Answer 6

Classification: type II topoisomerase, operates ahead of the replication fork by making a ds break, then covalently attaching ends to tyrosine residue so they are not lost before it can unwind and ligate back to together. Unlinks DNA after termination.

Question 7

What is Pol. I’s function in prokaryotes (3 features)

Answer 7

1)low-processivity polymerase that nick-translates IN OKAZAKI FRAG REGION at the RNA primer to degrade, then polymerize new DNA. 2) Has rare 5’ to 3’ exonuclease activity. 3) Pol I is the only proof-reading polymerase in prokaryotes.

Question 8

Where does termination occur in prokaryotes

Answer 8

directly across from OriC

Question 9

Mechanism of termination in prokaryotes

Answer 9

Tus protein (Directional filter for DnaB) binds 23 bp regions on either side of the termination site to push polymerases off if they arrive early. Gyrase unlinks new strands

Question 10

Which topoisomerase does the major part of unwinding in eukaryotes, what else does it do?

Answer 10

Type IIa (like gyrase in prokaryotes), also helps separate new chr from the old chr during mitosis

Question 11

What factors clean up the RNA primers in eukaryotes?

Answer 11

RNAase H, and FEN/RTH

Question 12

How and when do telomerases work?

Answer 12

Only expressed in somatic cells during development, they work by using an RNA template to synth repeats on the 3’ end on the lagging strand template (Reverse transcriptase)

Question 13

How do t-loops form? What structure do they assume?

Answer 13

Repetitive telomeric sequences fold back on themselves at the end of the chr, t loops form by the same complex that recruits telomerase- Shelterin. T-loops usually form G-quadruplexes.

Question 14

Why is telomerase not expressed?

Answer 14

It puts a check on cancer transformations, but unfortunately causes Hayflick limit