Lecture 2 DNA replication

Question 1

What is a false statement regarding DNA replication?

Answer 1

The only 3 enzymes required for DNA replication are DNA polymerase, helicase, and ligase

Question 2

DNA synthesis proceeds:

Answer 2

bidirectionally from the replication origin

Question 3

DNA replication begins

Answer 3

replication origions

Question 4

An enzyme that breaks, DNA dispels the tension, and reseals the strand ahead of a DNA replication growing fork is called a(n)

Answer 4

topoisomerase

Question 5

The Meseleson- Stahl experiment showed that:

Answer 5

DNA replication is semiconservative

Question 6

What is the function of the sliding loader?

Answer 6

opens the clamp and loads the clamp onto the ssDNA

Question 7

The sliding clamp:

Answer 7

is part of the replisome

Question 8

DNA synthesis:

Answer 8

utilizes energy obtained through hydrolysis of pyrophosphate

Question 9

Okazaki fragments are small fragments of DNA that eventually are ligated to form which of the following strands of DNA?

Answer 9

Lagging

Question 10

What are initiator proteins responsible for?

Answer 10

recruiting the helicase and stabilize the ssDNA

Question 11

The replication machinery:

Answer 11

moves along the DNA copying both strands

Question 12

How is torsional stress from supercoiling in replicating DNA revealed ahead of the replication fork?

Answer 12

Topoisomerase generates nicks in the DNA strand

Question 13

Which enzymes mediates the processing of Okazaki fragments?

Answer 13

ligase

Question 14

DNA ligase

Answer 14

catalyzed the formation of a phosphodiester bond

Question 15

Initiator Proteins - Prokaryotes

Answer 15

DnaA

Question 16

Initiator Proteins- Eukaryotes

Answer 16

ORC

Question 17

Helicase Prokaryotes

Answer 17

DnaB loaded onto ssDNA (5’-3’)

Question 18

Helicase eukaryotes

Answer 18

MCM complex loaded on dsDNA(3’-5’)

Question 19

Prokaryotes SSB (single stranded binding protein) - RPA Eukaryotes replication factor A

Answer 19

stabilizes and protects ssDNA, prevents helix reassociation and interacts with other proteins

Question 20

Topoisomerases Gyrase in prokaryotes and Topo I,II in eukaryotes

Answer 20

acts on dsDNA ahead of helicase, transiently creates nicks in DNA to relive torsional stress

Question 21

Ligase

Answer 21

seals nicks in Okazaki fragments (lagging strand)

Question 22

Primate (RNA polymerase)

Answer 22

primate in prokaryotes and alpha primate complex in eukaryotes it adds ~10bp RNA primer in 5’-3’ for DNA polymerase to bind to, part of primisome complex

Question 23

What is the sliding clamp?

Answer 23

stable ring, highly conserved, binds and keeps polymerase tethered to DNA remains until replication ends

Question 24

What is clamp loaders?

Answer 24

5 subunit structure, opens clamp and loads onto DNA, ATP hydrolysis binds clamp on DNA and releases loader removes clamp when replication finished

Question 25

What is holoenzyme?

Answer 25

3x core enzyme, 3x clamp, 1x loader