Why did hershey and chase label the viral dna with radioactive phosphorous and not radioactive sulfur?
dna contains phosphorus and no sulfur.
proteins contain phosphorus and no sulfur.
dna contains sulfur and little phosphorus. proteins contain sulfur and little phosphorus.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.