Question

Nitrogen and carbon are more abundant in proteins than sulfur. Why did Hershey and Chase use radioactive sulfur instead of nitrogen and carbon to label the protein portion of their bacteriophages in their experiments to determine whether parental protein or parental DNA is necessary for progeny phage production?

Answer 1

Radioactive sulfur and phosphorus were used to distinctly label T2 bacteriophage proteins and DNA, leading to the discovery that DNA is the genetic material in Chase and Hershey's 1952 experiments.

Step-by-step explanation:

In the groundbreaking Hershey-Chase experiments, radioactive sulfur (³⁵S) and radioactive phosphorus (³²P) were used to label proteins and DNA, respectively, in T2 bacteriophages. They chose radioactive sulfur to label the protein because sulfur is present in some amino acids (methionine and cysteine) that comprise proteins, but is not a component of nucleic acids.

Conversely, they used radioactive phosphorus to label the DNA because phosphorus is a key component of the DNA molecule but is not found in the amino acid structure of proteins. The conclusive experiment demonstrated that radioactivity from the labeled DNA, not the protein, was present inside the bacterial cells infected by the phages, thereby identifying DNA as the genetic material responsible for inheritance.

Answer 2

Hershey and Chase experiment confirms that DNA is the genetic material of the living organism, not the RNA or protein. They also got a noble prize for this discovery.

Hershey and Chase use the radioactive sulfur to label the proteins and distinguish them from the DNA because DNA do not contain sulfur. The radioactive label phosphorus was used to label the DNA as phosphorus is specific to DNA as they wants to know exactly the genetic material. They do not use the radioactive carbon and nitrogen because both carbon and nitrogen are present in DNA and RNA. This labeling may produce confused result as it label both DNA as well as protein. The result o radioactive phosphorus and sulfur determines that DNA is the genetic material of the organism.