Ultraviolet Radiation Damage & Repair pg. 727
What were the UV plates inoculated with?
Serratia marcescens
What does UV light penetrate poorly?
glass & plastic
What enzyme in the excision or dark repair process removes the nucleotides in the damaged strand?
helices
Long and intense exposure to UV produces more damage than the cell can...?
repair; thus there is less growth.
What has shorter, higher energy wavelengths than visible light?
ultraviolet radiation
How many enzymes are involved in excision repair or dark repair?
4: 1) endonuclease (aka ABC exinuclease) 2) helicase (aka helicese II) 3) DNA polymerase 1 4) DNA ligase
What enzyme in the excision or dark repair process forms a covalent bond between the new and original strands?
DNA ligase
What enzyme in the excision or dark repair process synthesizes a new strand?
DNA polymerase I
What do the pyrimidine dimers do to the DNA molecule?
Distort the DNA molecule & interfere with DNA replication/transcription
What organism performs photoreactivation, in which it repairs DNA damage?
Escherichia coli
What is the second repair mechanism that E. coli carries out to repair damaged DNA molecule from UV light?
Excision repair or dark repair
What is it called when the repair enzyme, DNA photolyase, is activated by visible light (300-500 nm) & monomerizes the dimer by reversing the original reaction?
Light repair or photo reactivation
What is the purpose of the UV test?
See the lethal effects of UV radiation; UV's ability to penetrate various objects; cells ability to repair damage
What happens when cells are exposed to UV light?
The DNA in the cells uses the energy from UV light to form new covalent bonds between adjacent pyrimidines: cytosine-cytosine, cytosine-thymine, thymine-thymine
What enzyme in the excision or dark repair process breaks 2 covalent bonds in the sugar-phosphate backbone of the damaged strand?
endonuclease
cytosine-cytosine, cytosine-thymine, thymine-thymine are called what?
pyrimidine dimers; thymine dimers are the most common
