Eukaryotic Replication and Telomeres

Question 1

What is a difference between eukaryotic and prokaryotic replication?

Answer 1

Eukaryotes use more than one origin of replication to replicate a linear chromosome.
Prokaryotes use a single origin of replication to replicate a circular chromosome.

Question 2

What is a unique challenge for eukaryotic replication?

Answer 2

Linear form of eukaryotic chromosome makes it impossible to completely replicate the lagging strand using RNA primers.

Question 3

Why can’t the lagging strand of eukaryotic DNA be completely replicated using RNA primers?

Answer 3

The last bit of RNA primer cannot be replaced with DNA because that would require the cell to put a primer without a template.

Question 4

What short sequence is repeated at the end of human chromosomes? Why?

Answer 4

GGGTTS repeated ~1000 times to attract telomerases

Question 5

What is telomerase?

Answer 5

Enzyme capable of binding to 3’ overhang at the incompletely replicated lagging strand, has an RNA molecule bound to a protein.

Question 6

What is the function of telomerase?

Answer 6

Its RNA is used to prime the addition of DNA to the 3’ overhang. Catalyzes the polymerization of DNA.

Question 7

What happens once telomerase makes the 3’ overhang long enough?

Answer 7

A more standard DNA polymerase is used to synthesize DNA at the end of the chromosome.

Question 8

What is telomerase an example of?

Answer 8

Reverse transcriptase

Question 9

What is reverse transcriptase?

Answer 9

An enzyme capable of synthesizing DNA using RNA as a template.