An artery a. brings blood back toward the heart b. has valves that prevent blood from flowing backward c. usually (but not always) carries oxygen-rich blood d. has thin, slightly elastic walls

In trying to determine whether dna or protein is the genetic material, hershey and chase made use of which of the following facts? a) dna contains sulfur, whereas protein does not. b) dna contains phosphorus, whereas protein does not. c) dna contains nitrogen, whereas protein does not. d) dna contains purines, whereas protein includes pyrimidines.