What happen to dna during sexual reproduction

How do the uv rays cause damage?   what exactly causes the skin to burn;   can you be more specific about this mechanism?   3. how do photosensitive medications increase a person's sensitivity to sunlight and therefore increase their risk of getting burned?     what kind of medications can increase photo-sensitivity, can you think of some examples?

When a person undergoes root canal treatment or another endodontic treatment: [select all that apply] a.) the inside of the tooth is carefully cleaned and disinfected. b.) air is forced into the canal to stop bleeding. c.) the inflamed/infected pulp is removed. d.) the inside of the tooth is filled and sealed with a rubber-like material called gutta-percha

In a study of a weight loss program, 40 subjects lost a mean of 3.0 lb after 12 months. does the weight loss program have practical significance? a. yes, because the weight loss program worked and the subjects lost a mean of 3.0 lb. b. no, because the mean weight loss of 3.0 lb after one year does not seem to justify the program. c. no, because the sample of 40 subjects was too small to determine if the program was useful. d. yes, because the mean weight loss of 3.0 lb after one year does seems to justify the program.