14.5: Eukaryotic Replication

Question 1

What 2 things makes Eukaryotic Replication complicated?

Answer 1

• The amount of DNA organized into multiple chromosomes

- The linear structure of chromosomes

Question 2

How do Eukaryotic cells reduce the time needed for replication?

Answer 2

-They use multiple origins for each chromosome= multiple Replicons

Question 3

What are the recognition of origins dependent on?

Answer 3

-Depends on chromatin structure and sequence

Question 4

What is the role of DNA Polymerase Epsilon?

Answer 4

-It is responsible for the leading strand synthesis

Question 5

What is the role of DNA Polymerase Delta?

Answer 5

-It synthesizes the lagging strand

Question 6

What is PCNA?

Answer 6

• AKA Poliferating(dividing) Cell Nuclear Antigen

- It is the sliding clamp subunit that allows the enzyme complex to stay attached

Question 7

What are the characteristics of PCNA?

Answer 7

• The sliding clamp forms a trimer

- Has similar structure and function to the B subunit sliding clamp

Question 8

What is the difference of synthesis of the Lagging Strand in Eukaryotes vs Prokaryotes?

Answer 8

• The Okazaki fragments are hella shorter= 200bp

- The displaced primer is removed by a nuclease & the remaining fragments are joined by ligase

Question 9

What does the Replisome require?

Answer 9

• DNA unwinding (helicase)
• Synthesis (primase & polymerase)
• Processivity factors (sliding clamps & their loaders)

Question 10

Which 2 life classes have the same subfamily of DNA polymerase enzymes?

Answer 10

• Eukaryotes

- Archea

Question 11

What is a key difference in the Replicative Helicases in bacterial & archeal/eukaryal enzymes?

Answer 11

-They are not Homologous & move in the opposite direction along the DNA

Question 12

What other component of Replisome is not homologous in bacteria & archeal/eukarya?

Answer 12

-The primase component of the replisome

Question 13

What is the function that is clearly homologous in ALL domains of life?

Answer 13

-The processivity factors= sliding clamps & clamp loaders

Question 14

What are Telomeres?

Answer 14

-They are the specialized structure on the ends of eukaryotic chromosomes

Question 15

What is the role of Telomeres?

Answer 15

• They protect the ends of chromosomes from nucleases

- They also maintain the integrity of linear chromosmes

Question 16

What are Telomeres made of?

Answer 16

• Specific DNA sequences

- NOT MADE by replication process

Question 17

What is the main problem of replicating the ends in Eukaryotes? what creates this problem?

Answer 17

• The very linear structure the chromosomes has

- The directionality of polymerases combined w/ their requirement for a primer

Question 18

What happens when the last primer of the 3’ end of the lagging strand is removed?

Answer 18

-It leaves a gap

Question 19

What problem does the gap poses at the 3’ end of the lagging strand? What would be the result?

Answer 19

• It cannot be primed= Polymerase complex cannot finish this end properly
• The result is gradual shortening of chromosomes w/ each round of cell division

Question 20

What is Telomerase?

Answer 20

-It is an enzyme that synthesizes telomeres on eukaryotic chromosomes using an internal RNA template to extend the DNA of the chromosome end

Question 21

What is the role of the internal RNA template in Telomerase?

Answer 21

-It allows short stretches of DNA to be synthesized= composed of repeated nucleotide sequences complementary to the RNA of the enzyme

Question 22

What happens when there is an absence of Telomere activity? at what age does this happen?

Answer 22

• The ends of the chromosome gradually shorten

- It usually happens during adulthood

Question 23

What is an aspect of cancer cells increasing their growth?

Answer 23

-They show activation of telomerase= maintain the telomere length

Question 24

What would be the result if there is an abnormal shortening of Telomeres/ lack of activity?

Answer 24

-It would affect the DNA that encodes important functions