Lecture 12- DNA Replication II

Question 1

Telomere

Answer 1

Region of repetitive DNA sequences at the end of a chromosome

Question 2

What is the end replication problem?

Answer 2

At the 5’ end the last RNA primer is removed on the lagging strand but can’t be replaces

Question 3

Telomerase function

Answer 3

Adds new enzyme sequence to ends of linear eukaryotic chromosomes
Only active in germ cella on most somatic body cells

Question 4

DNA pol I in E.coli

Answer 4

Helps remove RNA primer and replaces with DNA in chromosome replication
Role in repairing DNA

Question 5

DNA pol III in E.coli

Answer 5

Chromosome replication

Question 6

Role of E.coli DNA polymerases

Answer 6

Synthesis DNA and exonuclease activity

Question 7

3’-5’ exonuclease function

Answer 7

Degrades from the 3’ end and checks nucleotide has inserted correctly

Question 8

5’-3’ exonuclease function

Answer 8

Used to degrade the RNA primers at the end of Okazaki fragments

Question 9

Helices function

Answer 9

Unwinds the DNA duplex to form the replication fork

Question 10

DNA supercoiling advantages and disadvantages

Answer 10

Advantage- more compact
Disadvantage- difficulties in replication

Question 11

Positive DNA supercoiling

Answer 11

Right-handed double-helical formation of DNA twisted in a right-handed fashion (twisted tighter)
DNA overwound

Question 12

Negative DNA supercoiling

Answer 12

DNA twisted in left-handed fashion, looser coiling and twist taken out
DNA unwound

Question 13

Topoisomerase I function

Answer 13

Can remove both positive and negative supercoils
main function in DNA replication is removing negative supercoils (tightens underwound molecule)

Question 14

DNA Gyrase function

Answer 14

Removes positive supercoils (relaxes overwound molecule)

Question 15

Bacterial replication forks initiate at an …. and terminate at a ….

Answer 15

origin
terminus