Hershey and Chase's experiment

Hershey and Chase's experiment is the 1952 lab study that showed DNA, not protein, carries genetic information in a bacteriophage. In General Biology I, it is the classic proof that genes are made of DNA.

What is Hershey and Chase's experiment?

Hershey and Chase's experiment is the classic biology test that showed DNA is the hereditary material inside a virus called a bacteriophage. In General Biology I, you usually meet it in the history of genetics, right after Griffith's experiment and before the DNA structure lessons. The big question was simple: if a virus infects a bacterium, which part of the virus actually gets inside and passes along the instructions for making more viruses?

They worked with T2 bacteriophages, viruses that infect E. coli. This choice mattered because a phage is made of just two main parts, DNA and a protein coat, so it is easier to track than a whole cell with many molecules mixed together. Hershey and Chase labeled the DNA with radioactive phosphorus-32 and the protein with radioactive sulfur-35. That was a smart trick because DNA contains phosphorus in its backbone, while proteins contain sulfur in certain amino acids but DNA does not.

After the labeled phages infected bacteria, they used a blender to shake the viral coats off the bacterial cells and then spun the mixture in a centrifuge. The bacteria ended up in the pellet, while the empty phage coats stayed in the liquid. The phosphorus label, which marked DNA, was found inside the bacteria. The sulfur label, which marked protein, stayed outside.

That result meant the DNA entered the cell and carried the instructions for making new phages. The protein coat was basically a delivery shell. For biology, that was a huge shift because many scientists had assumed proteins were more likely to store genetic information, since proteins are made from 20 amino acids and can take on many shapes.

A common way to think about the experiment is as a molecular tracking problem. Hershey and Chase did not just say DNA was the genetic material, they followed the atoms to show where the genetic message actually went. That is why this experiment is remembered as direct evidence, not just a theory or a guess.

Why Hershey and Chase's experiment matters in General Biology I

Hershey and Chase's experiment matters because it answers one of the first big questions in molecular genetics: what molecule actually stores inheritance? Once you know that DNA is the genetic material, the rest of the unit starts to fit together more cleanly. DNA replication, transcription, translation, mutation, and gene expression all make more sense when DNA is the molecule carrying the instructions.

In General Biology I, this experiment also shows how scientists use evidence, not assumptions, to test a biological idea. Before this work, proteins seemed like the better candidate because they are more chemically varied than DNA. Hershey and Chase changed that view by designing an experiment that could separate the virus's DNA from its protein and track each one.

It also connects directly to later topics such as the structure of DNA and the central dogma. If you are asked why DNA became the focus of genetics, this experiment is one of the strongest historical reasons. It is also a good example of how radioactive labeling can be used as a lab method to trace a molecule's path through a system.

How Hershey and Chase's experiment connects across the course

Bacteriophage

The experiment used a bacteriophage, specifically T2, because a phage is small and simple enough to study as just DNA plus protein. That simplicity made it possible to ask which component entered the bacterial cell. If you know what a bacteriophage is, the logic of the experiment becomes much easier to follow.

Radioisotope labeling

Radioisotope labeling is the method Hershey and Chase used to tag DNA and protein with different radioactive atoms. The labels let them track where each molecule went after infection. In biology, this kind of labeling is a common way to follow molecules through a process instead of guessing based on structure alone.

DNA (Deoxyribonucleic Acid)

This experiment is one of the classic reasons DNA is treated as the genetic material in biology. It gives direct evidence that DNA carries the instructions for inheritance, not just a structural support role. That sets up later topics like DNA replication, genes, and mutation.

Griffith's experiment

Griffith's experiment came before Hershey and Chase and showed that some hereditary material could be transferred between bacteria, but it did not identify the molecule. Hershey and Chase built on that earlier mystery and showed that the inherited material was DNA. Together, the two experiments form the early evidence trail for modern genetics.

Is Hershey and Chase's experiment on the General Biology I exam?

A quiz question might ask you to identify which molecule Hershey and Chase proved was genetic material, or to read a diagram of the setup and interpret the phosphorus and sulfur labels. You may also need to explain why the blender and centrifuge were used, since those steps separated the bacterial cells from the viral coats. If you get a short-response prompt, focus on the logic of the experiment: DNA entered the bacteria, protein stayed outside, so DNA carried the genetic information. In lab or discussion, this term often shows up as part of the evidence chain for how scientists figured out what genes are made of.

Hershey and Chase's experiment vs Griffith's experiment

Griffith's experiment showed that a heritable factor could transfer between bacteria, but it did not identify what that factor was. Hershey and Chase later proved that the hereditary material was DNA by tracking radioactive labels in a bacteriophage. Griffith set up the question, and Hershey and Chase answered it.

Key things to remember about Hershey and Chase's experiment

• Hershey and Chase's experiment showed that DNA, not protein, is the genetic material in a bacteriophage.

• They used radioactive phosphorus-32 to label DNA and radioactive sulfur-35 to label protein, then tracked which label entered the bacteria.

• The DNA label ended up inside the bacterial cells, while the protein label stayed outside with the empty viral coats.

• The experiment is a major milestone in General Biology I because it connects heredity to DNA and sets up later genetics topics.

• If you remember one thing, remember the logic: the part that enters the cell and carries the instructions is the genetic material.

Frequently asked questions about Hershey and Chase's experiment

What is Hershey and Chase's experiment in General Biology I?

It is the 1952 experiment that showed DNA is the genetic material in a bacteriophage. By labeling DNA and protein with different radioactive isotopes, Hershey and Chase traced which molecule entered E. coli during infection.

Why did Hershey and Chase use phosphorus-32 and sulfur-35?

They needed two labels that would distinguish DNA from protein. DNA contains phosphorus in its backbone, while proteins can contain sulfur but DNA does not, so the isotopes let them track each molecule separately.

What is the difference between Hershey and Chase's experiment and Griffith's experiment?

Griffith showed that a heritable substance could move from one bacterium to another, but he did not identify the substance. Hershey and Chase later showed that the substance was DNA by following radioactive labels in a bacteriophage.

How do you explain Hershey and Chase's experiment in a lab report or exam answer?

State the question, describe the radioactive labeling, and explain the result. The DNA label entered the bacteria and the protein label stayed outside, so DNA must have carried the genetic information.