The Hershey-Chase experiment proved DNA is genetic material by using the isotopic marker ³²P, which labels DNA. They infected a bacterium where it replicated the ³²P as genetic material demonstrating DNA is genetic material.

DNA was first isolated from white blood cells by Friedrich Miescher, who called it nuclein because it was isolated from nuclei. Later experiments by Hershey and Chase using bacteriophages proved that DNA is genetic material. They did this by using a bacteriophage. They used two bacteriophages, one sample was produced in the presence of ³⁵S, which labelled the protein coat of the bacteriophage and the other sample was produced in the presence of ³²P, which label the DNA of the bacteriophage. When the bacteriophage injected its genetic material into host bacteria, Hershey and Chase found that only the ³²P entered the bacterial cells, indicating that DNA, not protein, is the genetic material.

Practice Questions

MCAT Official Prep (AAMC)

Practice Exam 4 B/B Section Question 9

Key Points

• Hershey and Chase established whether the phage injected DNA or protein into host bacteria. They prepared two samples of phage: ³⁵S, which labels protein and ³²P, which labels DNA. It was found that only ³²P entered the bacterial cells, indicating that DNA, not protein, is the genetic material.

Key Terms

DNA: deoxyribonucleic acid, a self-replicating material which is present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information

Bacteriophage:  A virus that parasitizes a bacterium by infecting it and reproducing inside it

Nuclein: Material from the nucleus of a cell, considered a single substance when first isolated in the late 1800s but later shown to consist of DNA and associated proteins.

Bacterium: A member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus