DNA Replication

Question 1

What is the function of single-strand binding protein in DNA replication?

Answer 1

Following unwinding of DNA by helicase, SSBs stabiles the single DNA strands, preventing hydrogen bonds from re-forming.

Question 2

What is the rate of DNA replication in eukaryotes and prokaryotes?

Answer 2

50 nucleotides/second in eukaryotes

500-1000 nucleotides/second in eukaryotes.

Question 3

In which direction can DNA polymerase synthesis a complementary DNA strand?

Answer 3

5’ to 3’ direction.

Question 4

What is the function of DNA gyrase in prokaryotes?

Answer 4

It ensures that DNA outside the replication fork does not supercoil.

Question 5

What is the frequency of error in DNA replication?

Answer 5

1 mistake in every 1 billion nucleotides.

Question 6

E. Coli cells grow in the 15N medium and are then transferred to 14N medium and allowed to grow for 2 more generations (two rounds of DNA replication). DNA extracted from these cells in centrifuged. What density of DNA would you expect in this experiment?

Answer 6

One intermediate density and one low density.

Question 7

The initiation of DNA synthesis by DNA polymerase requires:

• An RNA primer only
• DNA primer only
• RNA or DNA primer
• No primer

Answer 7

In-vivo only RNA primers are available and so only RNA primers are used
In-vitro, DNA or RNA primers may be used.