Alfred Day Hershey His best known

experiment is Hershey Chase experiment

Concerned the replication of genetic structure of viruses

4 Dec. 1908--- 22 May 1997

1934 -1950 Teaching and research at the Department of Bacteriology1936 Held an instructorship in bacteriology and immunology 1936 - 1939 Work together with Professor J. J. Bronfenbrenner. 1938 Became assistant professor 1942 Became associate professor

What is T2 ?What is T2 ?•The T2 phage is a strongly toxic bacteriophage and tadpole-shaped virus

• small virus that infect only bacteria

•Contain 50% DNA and 50% protein

•Contains linear double-stranded DNA

Infect E-coli

tail fibers of the phage attach to the bacterial cell to initiate infection

Protein coat of the T2 carries the organ of attachment to bacteria.

•Virus attach to the surface of their host cellVirus attach to the surface of their host cell (a)

The infective cycle of T2 in E.coil

•Inject the DNA into the cellInject the DNA into the cell (b)

•DNA accumulate,other genes are transcribed and translatedDNA accumulate,other genes are transcribed and translated (C)

•DNA and protein are assembled into complete virusDNA and protein are assembled into complete virus (d)

•The cell breaks and releases its content of virusThe cell breaks and releases its content of virus (e)

Hershey Chase Experiment Radioactive

Sulphur (35S)

non-radioative DNA?

Radioactive Phosphorous(35P)

radioactive DNA?