The timeline best illustrates that a) publication in scientific journals is necessary to expand any theory. b) peer review and publication is the basis for disproving early theories. c) scientific knowledge builds on prior knowledge; theories can be expanded. d) scientific knowledge builds on prior knowledge; theories are often disproved.

The hershey and chase experiments involved the preparation of two different types of radioactively labeled phage. which of the following best explains why two preparations were required? a. the bacteriophage used in the experiments was a t2 phage. b. it was necessary that each of the two phage components, dna and protein, be identifiable upon recovery at the end of the experiment. c. each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope. d. establishing the identity of the genetic material required observation of two phage generations.