Biochem 2 (DNA Replication and Repair)

Question 1

What is the autoantibody against topoisomerase and what disease is it associated with?

Answer 1

Anti-Sel-70 which is associated with diffuse scleroderma

Question 2

Which DNA polymerase is responsible for breakdown and replacement of the RNA primers on the lagging strand in prokaryotes?

Answer 2

DNA polymerase-I

Question 3

Which DNA polymerase synthesizes the lagging strand in eukaryotes?

Answer 3

DNA polymerase alpha

Question 4

Which DNA polymerase synthesizes the leading strand in eukaryotes?

Answer 4

DNA polymerase delta

Question 5

In eukaryotes, what is the function of DNA polymerase beta? gamma?

Answer 5

beta = DNA repair
gamma = Mitochondrial DNA replication

Question 6

What type of mutation causes sickle cell disease?

Answer 6

Non-conservative missense mutation (different amino acid sequence and protein structure)

Question 7

What is mismatch repair and a disease associated with defects in the pathway?

Answer 7

1)Improper nucleotides synthesized
2)Improper removed
3)Gap refilled and sealed
Hereditary non-polyposis colorectal cancer

Question 8

What are the enzymes involved in nucleotide excision repair (bulky lesions) and what is a disease associated with its defects?

Answer 8

1) Endonuclease - Removes nucleotides
2) DNA polymerase - Inserts nucleotides
3) DNA Ligase - Seals the gap
Xeroderma Pigmentosum

Question 9

What are the steps involved in base excision repair? Why is it needed?

Answer 9

1) Glycosolase - Removes the damaged base
2) Endonuclease - Cuts DNA
3) Polymerase - Fills gap
4) Ligase - Seals gap
Needed for repair of toxic/spontaneous deamination

Question 10

What are the features of ataxia telangiectasia and what defect is it caused by?

Answer 10

AT is caused by a defect in repair of dsDNA breaks. Its clinical features are cerebellar ataxia, telangiectasias, poor eye tracking, and IgA deficiency.