1. Hershey and Chase confirmed that DNA, and not protein, is the hereditary material.

2. In 1952, two researchers, Martha Chase and Alfred Hershey, set out to test whether DNA or protein was the hereditary material viruses transfer when viruses enter a bacterium. Bacteriophage - is a virus that infects bacteria.

3. Grew bacteriophage (with radioactive sulfur ) in dish of e.coli (sulfur is only found in proteins) Grew bacteriophage (with radioactive phosphorous ) in dish of e.coli (phosphorous is only found in DNA) They traced the radioactive elements that had entered the e.coli …to see which one was injected into the cell. The DNA of the virus and not the proteins was what was in the e.coli causing it to produce more viral DNA.

5. Hershey and Chase confirmed that DNA, and not protein, is the hereditary material.

6. Griffith’s experiments showed that hereditary material can pass from one bacterial cell to another.

7. In 1928 Griffith was studying a bacterium called Streptococcus pneumoniae. He was trying to develop a vaccine against a virulent strain of the bacterium. Virulent – ability disease causing Vaccine – a substance that is prepared from killed or weakened microorganisms & introduced into the body to protect it from future infection by that microorganism.

8. S bacteria is virulent because it has a capsule. The capsule protects it from attacks by the human immune system. It is able to survive long enough in the human body to replicate and cause disease. R bacteria is NOT virulent because it lacks a capsule. Without the capsule it is left defenseless against the human immune system. Therefore it is destroyed in the human body before it is able to cause disease.

9. Injected mouse with live R bacteria (w/o capsule). NOT Killed mice Injected mouse with live S bacteria (w/ capsule). kill mice Injected mouse with heat killed S bacteria. NOT kill mice Injected mouse with heat killed S bacteria mixed with live R bacteria. Killed mice

11. The R bacteria took up the DNA found in the heat killed S bacteria and became virulent! The transfer of genetic material from one cell to another cell or from one organism to another organism is called transformation.