DNA Replication And Repair Flashcards Preview

Biochemestry and Medical Genetics > DNA Replication And Repair > Flashcards

Flashcards in DNA Replication And Repair Deck (10):
1

What is the difference between exonuclease and endonuclease?

- Exonuclease: remove nucleotides
- Endonuclease: release nucleic acid fragments
(Both hydrolyze PDE bonds)

2

Mention 3 differences between replication and synthesis of RNA

- "Proofreading" - DNA pol does (exonuclease 3'➡️5'), RNA pol doesn't
- Primer - DNA pol need it, RNA pol doesn't
- Substrates - dMNP for DNA pol, MNP for RNA pol

3

Facts in common between replication and RNA synthesis

- New strand synthesized 5'➡️3'
- Template strand scanned 3'➡️5'
- New strand complementary and antiparallel to the template

4

What do the quinolones, acid nalidixic (in bacterias) and etoposide, teniposide (in eukaryotic) share based on their mechanism of action?

*Block and inhibit the prokaryotic topoisomerase II (DNA gyrase) - bacteria
*Inhibit eukaryotic topoisomerase II - anticancer drugs

5

Why are the cancer cells immortals based on their chromosomes and replication?

They have high levels of Telomerase - avoid shortened of the telomeres

6

How does the AZT prevent further replication causing chain termination?

Replacement of azide instead normal OH group at 3' of the deoxyribose. (Reverse transcriptase not proofreading)

*other drugs inhibiting DNA synthesis by reverse transcriptase in HIV - ddC, ddI

7

In what cases does the eukaryotic cells have reverse transcriptase activity?

*Telomerase (hTRT)
*Encoded by retrotransposons - amplify certain repetitive sequences in DNA

8

What is the cause of Xeroderma Pigmentosum? Symptoms.

- Deficiency of Excision Endonnuclease
- symptoms:
* excessive freckling
* extreme UV sensitivity
* multiple skin cancer
* corneal ulcerations

9

What type of damage is not corrected in Hereditary nonpolyposis colorectal cancer (HNPCC)? Why?

Mismatch base - because inherited and somatic mutation of hMLH1 or hMSH2 (make DNA mismatch repair - detect and remove errors during replication)

10

Ultimately what type of error of the replication we can see in HNPCC?

Microsatellite instability