Test1: Lect2 Maureen Hoatlin

Question 1

Topiosomerases:

• Also called:
• What do they do?

Answer 1

• Also called:
  Gyrases
• What do they do?
  Cut and unwind strands

Question 2

How is the replication problem solved?

- What does the end of a chromosome look like?

Answer 2

Telomerase!

• What does the end of a chromosome look like?
  1: G-T rich strand that extends beyond a C-A-rich strand
  2: These loop around and the extended single stranded G-T rich domain binds with the C-A rich repeat

Question 3

Telomerase:

• Does what:
• Structure:

Answer 3

• Does what:
  Extends the telomeres by adding more G’s and T’s to the repeat sequence.
• Structure:
  1: They are made of many proteins
  2: lot of repair proteins are located there.

Question 4

Which three polymerases are used in eukaryotic replication:

• Low fidelity:
• High fidelity:

Answer 4

• Low fidelity:
  1: DNA pol alpha (initiates new strand synthesis of lagging)
  2: no 5’ to 3’ exonuclease (proofreading)
• High fidelity:
  1: DNA pols epsilon and delta:
  1: Elongation
  2: have 5’ to 3’ exonuclease (proofreading)

Question 5

Disparity mutagenesis:

- Implication:

Answer 5

That lagging strands are more likely to have errors because of new more use of polymerase alpha on the lagging strand.
- Implication:
Housekeeping genes which are important are kept on leading strand. Genes where it’d be advantageous to mutate them are kept on lagging strand

Question 6

DNA polymerase epsilon:

• Primarily involved on?
• Low or hifi?

Answer 6

• Primarily involved on?
  Leading strand synthesis
• Low or hifi?
  High fidelity

Question 7

DNA polymerase delta:

• Primarily involved on?
• Low or hifi?

Answer 7

• Primarily involved on?
  Lagging strand synthesis
• Low or hifi?
  High fidelity

Question 8

Why are there so many polymerases in eukaryotes?

Answer 8

They are used to bypass specific errors in DNA synthesis.
PCNA meets some form of legion, it grabs a specific polymerase, such as a translesion polymerase, which can bypass the damage

Question 9

What does a defective Pol eta (eta is a greek letter) cause?

• Why?
• What is pol eta?
• Are post-translation DNA repair mechanisms intact in these individuals?

Answer 9

Xeroderma Pigmentosum
- Why?
Xeroderma Pigmentosum is a large array of skin cancer.
Results from inability to bypass certain damage during replication. Likely pyradimine dimers.
- What is pol eta?
A translesion polymerase
- Are post-translation DNA repair mechanisms intact in these individuals?
Yes