Lab 23

Question 1

in what ways does radiation differ?

Answer 1

in wavelength and energy

Question 2

x rays and gamma rays are forms of:

Answer 2

ionizing radiation

Question 3

principal effect is to ionize water into highly reactive free radicals that can break strands of DNA

Answer 3

ionizing radiation

Question 4

Some ______ wavelengths are essential for biochemical processes.

Answer 4

nonionizing

Question 5

nonionizing radiation between 15 and 400 nm

Answer 5

ultraviolet (UV)

Question 6

most lethal wavelengths are sometimes called ____, and are in the _____ range

Answer 6

biocidal, UVC

Question 7

range 200-290nm and wavelengths corresponding to the optimal absorption wavelengths of DNA

Answer 7

UVC

Question 8

____ wavelengths 290-320 nm can also cause damage to DNA

Answer 8

UVB

Question 9

____ wavelengths 320-400 nm are not as readily absorbed and are therefore less active on living organisms

Answer 9

UVA

Question 10

UV light induces _____ in DNA which results in a mutation

Answer 10

thyamine dimers

Question 11

repair mechanism where thyamine dimers are exposed to visible light, photolyases are activated; these enzymes split the dimers, restoring the DNA to its undamaged state

Answer 11

light repair, photoreactivation

Question 12

Another repair mechanism, _______, is independent of light. Dimers are removed by endonuclease, DNA polymerase replaces the nucleotides, and DNA ligase seals the sugar-phosphate backbone

Answer 12

dark repair