Lab 7

Question 1

Whats the effect of UV on DNA

Answer 1

causes dimers between adjacent DNA molecules -> affects transcription , replciationdistortion

-> long term damage can cause irreparable damage.

Question 2

What are the repair mechanisms

Answer 2

Light repair (photoreactivation)

and dark repair (excision repair)

Question 3

How does light repair work

Answer 3

The enzyme photolyase is activated by visible light in E. coli

monomerize the dimer by reversing the original reaction.

Steps:
1. UV irradiation

2. Photolyase binds to the dimer
3. Cleaves the cross link
4. releases the enzyme

Question 4

Dark and light repair mechanisms can repair

Answer 4

small amounts of damange resulting from short exposuer times. But cannot repair longer exposure to UV radiation

Question 5

How does dark repair work

Answer 5

exision.

an endonucleaus breaks 2 covalent bonds upstream and downstream of the the dimer

helicase removes the damanged fragmeent.

DNA polymerase sysnthesiszies a new strand

Ligagse forms covalent bond