AP BIOLOGY

Detailed explanation-1: -In 1952, Alfred Hershey and Martha Chase took an effort to find the genetic material in organisms. Their experiments led to an unequivocal proof to DNA as genetic material. Bacteriophages (viruses that affect bacteria) were the key element for Hershey and Chase experiment.

Detailed explanation-2: -Hershey and Chase were able to separate the phages into radioactive sulfur-containing protein ghosts and radioactive phosphorus-containing DNA. They found that the radioactive sulfur protein ghosts could attach to bacterial membranes while the radioactive phosphorus DNA could not.

Detailed explanation-3: -Hershey and Chase found that when bacteriophages containing 32P (radioactive), were allowed to infect nonradioactive bacteria, all the infected cells became radioactive and, in fact, much of the radioactivity was passed on to the next generation of bacteriophages.

Detailed explanation-4: -Hershey and chase use radioactive sulfur and phosphorus to mark the molecules of interest. As these radioactive elements emit radioactivity, they can be traced. Radioactive sulfur was used to mark proteins as DNA doesn’t have sulfur. Radioactive phosphorus was used to mark DNA as proteins doesn’t have phosphorus.