Exam 2 Part 2 Flashcards
UV is a type of what
electromagnetic energy
this is the distance between adjacent wave crests, measured in nm
wavelength
what are the three categories of ultraviolet light
UV A (315-400 nm), UV B (280-315 nm), UV C (100-280 nm)
what wavelength is the most detrimental
exposure to this for more than a few min usually results in damage or death
UV C
what is the germicidal effect related to
time of exposure, lamp intensity, and distance to the target
what is effectiveness diminished by
dust
what is ultra violet light commonly used for
to disinfect labs and health care environments
why is prolonged exposure lethal
DNA absorbs UV radiation at 254 nm the energy is used to form new covalent bond between adjacent pyrimidines
what are the pyrimidine dimers
cytosine-cytosine, cytosine-thymine, thymine-thymine
what do the pyrimidine dimers do
distort the DNA molecule and interfere with DNA replication and transcription
what is light repair also known as
photoreactivation
when is the repair enzyme activated by visible light and reverses the original reaction
light repair
what is the repair enzyme
DNA photolyase
what is dark repair also known as
excision repair(involves multiple enzymes)
what enzymes does dark repair include
endonuclease, helicase, DNA polymerase 1, and DNA ligase
what does the endonuclease do
breaks two covalent bond in backbone
what does helicase do
removes the nucleotides in the damaged segment
what does DNA polymerase do
synthesizes the new strand