Sickle cell disease is caused by a:

a. change in one allele.

b. change in the size of a chromosome.

c. change in two proteins.

d. change in the number of chromosomes in a cell.

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.