Mod3 - Genomes

Question 1

How many origins of replication does E. coli have?

Answer 1

1 (always in same position on genome)

Question 2

How many origins of replication are there in human DNA?

Answer 2

Multiple origins on each chromosomal DNA molecule (more than one required because otherwise it would take too long -> more DNA than in prokaryotes)

Question 3

How does replication begin at the origin in E. coli?

Answer 3

DnaA proteins bind close to the origin of replication, which is AT-rich (weak), so base pairs break. DnaB helicase then breaks base pairs apart to move the replication fork away from the origin (bidirectional)

Question 4

What is the role of the gamma complex in DNA Replication?

Answer 4

In prokaryotes, the gamma complex attaches and detaches DNA Pol III to and from the lagging strand

Question 5

What is the role of the beta complex in DNA Replication?

Answer 5

In prokaryotes, the beta complex holds DNA Pol III onto the template strand, allowing it to slide

Question 6

What is the name of the sliding clamp that holds DNA Pol delta onto the DNA in eukaryotes?

Answer 6

Proliferating Cell Nuclear Antigen (PCNA)

Question 7

What removes the primers and joins the Okazaki fragments in prokaryotes?

Answer 7

DNA Pol I and DNA ligase

Question 8

What removes the primers and joins the Okazaki fragments in eukaryotes?

Answer 8

FEN1 and DNA ligase

Question 9

What is the structure of a nucleosome?

Answer 9

A nucleosome is an octamer made up of 8 histones (2 each of H2A, H2B, H3 and H4)

Question 10

What is the role of H1 in chromatin?

Answer 10

It is a linker histone