Cell bio

Question 1

What is the function of topoisomerases?

Answer 1

reduce DNA supercoiling by introducing breaks, negative coiling and ligation of the breaks

Question 2

What are two major features of heterocromatin? What is the key consequence of these features?

Answer 2

heavily methylated DNA
deacetylated histones

low transcriptional activity

Question 3

What is more likely to introduce faulty repair, double or single stranded DNA breaks?

Answer 3

double

Question 4

hereditary non-polyposis colorectal cancer is associated with impaired _____

Answer 4

mismatch repair

Question 5

what enzyme is responsible for unwinding the double helix?

Answer 5

helicase

Question 6

what removes supercoils in prokaryotic DNA replicaiton?

Answer 6

topoisomerase II (DNA gyrase)

Question 7

what facilitates the stabilization of unwound template strands of DNA during prokaryotic DNA replication?

Answer 7

dingle stranded DNA-binding proteins

Question 8

what enzyme synthesis the RNA during prokaryotic DNA replication?

Answer 8

primase (aka RNA polymerase)

Question 9

what facilitatees 5’ to 3’ DNA synthesis and also has 3’ to 5’ exonuclease “proofreading” activity during prokaryotic DNA replication?

Answer 9

DNA polimerase I and III

Question 10

What removes teh RNA primer (5’ to 3’ exonuclease acvity) and replaces it with DNA during prokaryotic DNA replication??

Answer 10

DNA polimerase I

Question 11

what joinds the okazaki graments (lagging strand) during prokaryotic DNA replication?

Answer 11

DNAse liga

Question 12

what is required for DNA polimerase III to begin 5’=>3’ synthesis of DNA?

Answer 12

RNA primer