the hershey chase experiment this is an image of a

The Hershey-Chase Experiments (1952), by Alfred Hershey and Martha Chase

In 1951 and 1952, Alfred Hershey and Martha Chase conducted a series of experiments at the Carnegie Institute of Washington in Cold Spring Harbor, New York, that verified genes were made of deoxyribonucleic acid, or DNA. Hershey and Chase performed their experiments, later named the Hershey-Chase experiments, on viruses that infect bacteria, also called bacteriophages. The experiments followed decades of scientists’ skepticism about whether genetic material was composed of protein or DNA. The most well-known Hershey-Chase experiment, called the Waring Blender experiment, provided concrete evidence that genes were made of DNA. The Hershey-Chase experiments settled the long-standing debate about the composition of genes, thereby allowing scientists to investigate the molecular mechanisms by which genes function in organisms.

In the early twentieth century, scientists debated whether genes were made of DNA or protein. Genes control how organisms grow and develop and are the material basis for organisms’ ability to inherit traits like eye color or fur color from their parents. By 1900, scientists had identified the complete chemical composition, or building blocks, of DNA. They had also verified that all cells contained DNA, though DNA’s function remained ambiguous. Up until the 1940s, some scientists accepted the idea that genes were not made of DNA. Instead, those scientists supported the idea that DNA was a molecule that maintained cell structure. Scientists supported that idea in part because of a hypothesis called the tetranucleotide hypothesis. Phoebus Levene, a researcher at the Rockefeller Institute for Medical Research in New York City, New York, proposed the tetranucleotide hypothesis for DNA in 1933. According to Levene and other proponents of the hypothesis, DNA consisted of repeating sets of four different building blocks, called nucleotides. Some scientists concluded that a repeating sequence of nucleotides in DNA limited potential for variability. Those scientists considered variability necessary for DNA to function as genetic material. In other words, genes needed to have the capacity for enough variation to account for the different traits scientists observe in organisms. Conversely, scientists found that proteins had many more building blocks and therefore more possible arrangements than DNA. From that, some scientists claimed that genes must have been made of protein, not DNA.

The Hershey-Chase experiments were not the first studies to oppose the prevailing theory in the early 1900s that genetic material was composed of proteins. In 1944, nearly a decade before Hershey and Chase’s work, scientists published sound evidence that genes were made of DNA rather than protein. Starting in 1935, Oswald Avery, another researcher at the Rockefeller Institute, with his research associates Colin MacLeod and Maclyn McCarty, performed experiments that showed that DNA facilitated a genetic phenomenon in bacteria called bacterial transformation. Bacterial transformation is the process by which a bacterium can get and use new genetic material from its surroundings. During bacterial transformation, a non-disease-causing bacterium can transform into disease-causing bacteria if the non-disease-causing bacteria is exposed to a disease-causing bacteria. Transformation can occur even if the disease-causing-strain is dead, implying that bacterial transformation happens when the non-disease-causing bacteria inherits genetic material from the disease-causing bacteria. Avery and his colleagues found that the inherited factor that caused bacterial transformation contained DNA. However, Avery’s group did not discount the possibility that some non-DNA component in their sample caused bacterial transformation, rather than the DNA itself. Because of that, many scientists maintained the idea that proteins must govern the genetic phenomenon of bacterial transformation.

Starting in 1951, Alfred Hershey and Martha Chase conducted a series of experiments, later called the Hershey-Chase experiments, that verified the findings of Avery and his colleagues. Hershey was a researcher who studied viruses at the Carnegie Institution of Washington in Cold Spring Harbor, New York. He studied viruses that infect bacteria, also called bacteriophages, or phages. Chase became Hershey’s research technician in 1950.

In their experiments, Hershey and Chase analyzed what happened when phages infect bacteria. By the 1950s, scientists had evidence for how phages infected bacteria. They found that when phages infect a host bacterium, the phages first attach themselves to the outside of the bacterium. Then, a piece of the phage enters the bacterium and subsequently replicates itself inside the cell. After many replications, the phage causes the bacterium to lyse, or burst, thereby killing the host bacteria. Scientists classified the replicating piece as genetic material. Scientists also found that phages contained two classes of biological molecules: DNA and protein. Hershey and Chase sought to determine if the replicating piece of phages that entered bacteria during infection, the genetic parts, were solely DNA.

To perform their experiments, Hershey and Chase utilized a technique called radioactive isotope labeling. Chemical elements can exist in different structural forms called isotopes. Isotopes of the same element are nearly identical, but scientists can distinguish between them by experimental means. One way to differentiate between chemical elements with different isotopes is by analyzing their radiation. Some isotopes are less stable than others and give off radioactive signals that scientists can detect. Hershey and Chase marked phages by incorporating radioactive isotopes of phosphorus and sulfur in those phages. They allowed some phages to replicate by infecting bacteria, specifically Escherichia coli , or E. Coli , that scientists had grown in radioactive sulfur. The researchers let other phages infect and replicate in E. Coli that scientists had grown in radioactive phosphorus. DNA contains phosphorus, but not sulfur, whereas protein contains sulfur, but not phosphorus. Therefore, when Hershey and Chase marked phages with radioactive isotopes of those elements, they placed separate, distinguishable tags on the protein and DNA parts of the phages.

The first Hershey-Chase experiment aimed to confirm previous experimental findings that the DNA and protein components of phages were separable. In 1950, Thomas Anderson at the University of Pennsylvania in Philadelphia, Pennsylvania, showed that phages consisted of a protein shell, or coat, with DNA inside the shell. Anderson found that the phages could release their DNA and leave behind what he called a protein ghost. Hershey and Chase replicated Anderson’s experimental results using their radioactive isotope labeling method. 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. Hershey and Chase also tested if enzymes, molecules that facilitate chemical reactions in cells, could degrade DNA. They found that enzymes did not degrade the DNA of intact phages, but did degrade the DNA of separated phages. Those results indicated that in the intact phages, the protein coat surrounded the DNA and protected the DNA from degradation.

In another Hershey-Chase experiment, Hershey and Chase showed that when certain phages infected E. Coli , the phages injected their DNA into the host bacterium. In 1951, Roger Herriot at Johns Hopkins University in Baltimore, Maryland, demonstrated that after phages infected bacteria, their protein ghosts remained attached to the outside of the bacterial cells while their DNA was released elsewhere. Hershey and Chase aimed to show where the phage DNA went when it exited the protein coat and entered the bacteria. The researchers allowed radioactive phosphorus-labeled phages to attach to bacterial cell membranes in a liquid solution and infect the bacteria. Using a centrifuge, Hershey and Chase rapidly spun the samples to separate the bacterial cells from the surrounding solution. After centrifugation, they found that most of the radioactive phosphorus was detected in the cells rather than in the surrounding solution, meaning that the phage DNA must have entered the cells when the phages infected the bacteria.

The most well-known Hershey-Chase experiment was the final experiment, also called the Waring Blender experiment, through which Hershey and Chase showed that phages only injected their DNA into host bacteria, and that the DNA served as the replicating genetic element of phages. In the previous experiment, Hershey and Chase found evidence that phages injected their DNA into host bacteria. In the Waring Blender experiment, the scientists found that the phages did not inject any part of their protein coats in the host bacteria and the protein coats remained outside the bacteria, adhered to the bacterial membranes. For their experiment, Hershey and Chase prepared two samples of infected E. Coli . They infected one sample with radioactive phosphorus-labeled phages, and the other sample with radioactive sulfur-labeled phages. Then, they stirred each sample in a Waring Blender, which was a conventional kitchen blender. They used a blender because centrifuges spun too fast and would destroy the bacterial cells. The shearing forces of the blender removed the phage particles that adhered to the bacterial membranes, but preserved the integrity of the cells and most of the phage material that entered the cell. In the phosphorus-labeled sample that marked DNA but not protein, the blender removed forty percent of the labeled particles. In the sulfur-labeled sample that marked protein but not DNA, the blender removed eighty percent of the labeled particles. Those results indicated that the blender removed much more of the protein parts of the phage than the DNA parts, suggesting that the protein likely remained adhered to the outside of the cell during infection. Since the protein remained outside the cell, it could not be the replicating genetic material.

The Waring Blender only removed eighty percent of the radioactive sulfur-labeled phage, so Hershey and Chase could not account for twenty percent of the phage protein material. To show that the missing twenty percent of the phage protein did not enter the bacterial cells and replicate, the researchers infected E. Coli with radioactive sulfur-labeled phage again so that only the protein parts of the phage were labeled. They prepared two samples. For one sample, Hershey and Chase stirred the cells in the blender to remove the phage particles adhered to the outer bacterial membrane. After stirring, they allowed the phages to cause the cells to lyse, releasing newly replicated phages. For the second sample, Hershey and Chase did not stir the cells in the blender and measured the resulting replicated phages after the bacterial cells lysed. In the blender-stirred sample, less than one percent of the replicated phages contained the radioactive sulfur label. However, in the sample that Hershey and Chase did not stir in the blender, almost ten percent of the phages contained the radioactive sulfur label. The blender maintains any phage material that entered the bacterial cell. If protein was genetic material that entered the cell and replicated, then Hershey and Chase would have found more sulfur-labeled protein in the sample they stirred with the blender. The sample that they did not stir had more of the sulfur-labeled protein because the protein coats remained on the outside of the cell. Hershey and Chase concluded that protein was not genetic material, and that DNA was genetic material.

Unlike Avery’s experiments on bacterial transformations, the Hershey-Chase experiments were more widely and immediately accepted among scientists. The Hershey-Chase experiments mostly ended scientists’ suspicions that genes were made of protein rather than DNA. However, historians have questioned the conclusiveness of the Hershey-Chase experiments. In all the Waring Blender experiments, some protein and DNA material remained unaccounted for. Even in the final experiment, when Hershey and Chase allowed the bacterial cells to lyse after stirring in the blender, the scientists still recovered a small amount of protein, implying that some protein entered the cells during infection. Furthermore, the amount of contaminating protein in the Hershey-Chase Experiments exceeded the amount of contaminating protein that Avery’s group found in their experiments.

Historians of science have studied why scientists more readily accepted the Hershey-Chase experiments than Avery’s experiments. Science historian Frederic Lawrence Holmes writes that scientists more readily accepted the results of the Hershey-Chase experiments because Hershey communicated directly with skeptical scientists. Hershey sent letters to his colleagues in which he detailed the experimental findings of the Hershey-Chase experiments. Another historian of science, Michel Morange, writes that the Hershey-Chase experiments were performed at a time when scientists were ready to accept that genetic material could be DNA. Avery’s group conducted their experiments when the tetranucleotide hypothesis was popular and few scientists held that genes contained DNA. According to Morange, because Hershey and Chase conducted their experiments years later, scientists had gathered more experimental evidence and were willing to seriously consider that genes contained DNA.

In 1953, James Watson and Francis Crick, two scientists at the University of Cambridge in Cambridge, England, modeled the three-dimensional structure of DNA and demonstrated how DNA might function as genetic material. In 1969, Hershey shared the Nobel Prize in Physiology or Medicine with two other scientists, Max Delbrück and Salvador Luria, partly for his work on the Hershey-Chase experiments.

• Avery, Oswald, Colin MacLeod, and Maclyn McCarty. "Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types." The Journal of Experimental Medicine 79 (1944): 137–58.
• Fry, Michael. “Chapter 4 – Hershey and Chase Clinched the role of DNA as Genetic Material: Phage Studies Propelled the Birth of Molecular Biology.” In Landmark Experiments in Molecular Biology , 111–42. Cambridge: Academic Press, 2016.
• Hershey, Alfred D., and Martha Chase. “Independent Functions of Viral Protein and Nucleic Acid in Growth of Bacteriophage” The Journal of General Physiology 36 (1952): 39–56.
• Holmes, Frederic L. Meselson, Stahl, and the Replication of DNA: A History of “The Most Beautiful Experiment in Biology.” New Haven and London: Yale University Press, 2001.
• Hopson, Janet L., and Norman K. Wessells. Essentials of Biology . New York: McGraw-Hill, 1990.
• Judson, Horace Freeland. The Eighth Day of Creation . Cold Spring Harbor: Cold Spring Harbor Laboratory Press, 1996.
• Morange, Michel. A History of Molecular Biology . Cambridge and London: Harvard University Press, 1998.
• Olby, Robert Cecil. The Path to the Double Helix: The Discovery of DNA . Seattle: University of Washington Press, 1974.
• Stahl, Franklin W., and Alfred D. Hershey. We Can Sleep Later: Alfred D. Hershey and the Origins of Molecular Biology . Woodbury: Cold Spring Harbor Laboratory Press, 2000.

How to cite

Articles rights and graphics.

Copyright Arizona Board of Regents Licensed as Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported (CC BY-NC-SA 3.0)  

Last modified

Share this page.

Microbe Notes

DNA Experiments (Griffith & Avery, McCarty, MacLeod & Hershey, Chase)

DNA, deoxyribonucleic acid, is the carrier of all genetic information. It codes genetic information passed on from one generation to another and determines individual attributes like eye color, facial features, etc. Although DNA was first isolated in 1869 by a Swiss scientist, Friedrich Miescher, from nuclei of pus-rich white blood cells (which he called nuclein ), its role in the inheritance of traits wasn’t realized until 1943. Miescher thought that the nuclein, which was slightly acidic and contained a high percentage of phosphorus, lacked the variability to account for its hereditary significance for diversity among organisms. Most of the scientists of his period were convinced by the idea that proteins could be promising candidates for heredity as they were abundant, diverse, and complex molecules, while DNA was supposed to be a boring, repetitive polymer. This notion was put forward as the scientists were aware that genetic information was contained within organic molecules.

Table of Contents

Interesting Science Videos

Griffith’s Transformation Experiment

In 1928, a young scientist Frederick Griffith discovered the transforming principle. In 1918, millions of people were killed by the terrible Spanish influenza epidemic, and pneumococcal infections were a common cause of death among influenza-infected patients. This triggered him to study the bacteria Streptococcus pneumoniae and work on designing a vaccine against it . It became evident that bacterial pneumonia was caused by multiple strains of S. pneumoniae, and patients developed antibodies against the particular strain with which they were infected. Hence, serum samples and bacterial isolates used in experiments helped to identify DNA as the hereditary material. 

He used two related strains of S. pneumoniae and mice and conducted a series of experiments using them. 

• When type II R-strain bacteria were grown on a culture plate, they produced rough colonies. They were non-virulent as they lacked an outer polysaccharide coat. Thus, when RII strain bacteria were injected into a mouse, they did not cause any disease and survived.
• When type I S-strain bacteria were grown on a culture plate, they produced smooth, glistening, and white colonies. The smooth appearance was apparent due to a polysaccharide coat around them that provided resistance to the host’s immune system. It was virulent and thus, when injected into a mouse, resulted in pneumonia and death. 
• In 1929, Griffith experimented by injecting mice with heat-killed SI strain (i.e., SI strain bacteria exposed to high temperature ensuing their death). But, this failed to harm the mice, and they survived.
• Surprisingly, when he mixed heat-treated SI cells with live RII cells and injected the mixture into the mice, the mice died because of pneumonia. Additionally, when he collected a blood sample from the dead mouse, he found that sample to contain live S-strain bacteria.

Conclusion of Griffith’s Transformation Experiment

Based on the above results, he inferred that something must have been transferred from the heat-treated S strain into non-virulent R strain bacteria that transformed them into smooth coated and virulent bacteria. Thus, the material was referred to as the transforming principle.

Following this, he continued with his research through the 1930s, although he couldn’t make much progress. In 1941, he was hit by a German bomb, and he died.

Avery, McCarty, and MacLeod Experiment

During World War II, in 1943, Oswald Avery, Maclyn McCarty, and Colin MacLeod working at Rockefeller University in New York, dedicated themselves to continuing the work of Griffith in order to determine the biochemical nature of Griffith’s transforming principle in an in vitro system. They used the phenotype of S. pneumoniae cells expressed on blood agar in order to figure out whether transformation had taken place or not, rather than working with mice. The transforming principle was partially purified from the cell extract (i.e., cell-free extract of heat-killed type III S cells) to determine which macromolecule of S cell transformed type II R-strain into the type III S-strain. They demonstrated DNA to be that particular transforming principle.

• Initially, type III S cells were heat-killed, and lipids and carbohydrates were removed from the solution.
• Secondly, they treated heat-killed S cells with digestive enzymes such as RNases and proteases to degrade RNA and proteins. Subsequently, they also treated it with DNases to digest DNA, each added separately in different tubes.
• Eventually, they introduced living type IIR cells mixed with heat-killed IIIS cells onto the culture medium containing antibodies for IIR cells. Antibodies for IIR cells were used to inactivate some IIR cells such that their number doesn’t exceed the count of IIIS cells. that help to provide the distinct phenotypic differences in culture media that contained transformed S strain bacteria.

Observation of Avery, McCarty, and MacLeod Experiment

The culture treated with DNase did not yield transformed type III S strain bacteria which indicated that DNA was the hereditary material responsible for transformation. 

Conclusion of Avery, McCarty, and MacLeod Experiment

DNA was found to be the genetic material that was being transferred between cells, not proteins.

Hershey and Chase Experiment

Although Avery and his fellows found that DNA was the hereditary material, the scientists were reluctant to accept the finding. But, not that long afterward, eight years after in 1952, Alfred Hershey and Martha Chase concluded that DNA is the genetic material. Their experimental tool was bacteriophages-viruses that attack bacteria which specifically involved the infection of Escherichia coli with T2 bacteriophage.

T2 virus depends on the host body for its reproduction process. When they find bacteria as a host cell, they adhere to its surface and inject its genetic material into the bacteria. The injected hereditary material hijacks the host’s machinery such that a large number of viral particles are released from them. T2 phage consists of only proteins (on the outer protein coat) and DNA (core) that could be potential genetic material to instruct E. coli to develop its progeny. They experimented to determine whether protein or DNA from the virus entered into the bacteria.

• Bacteriophage was allowed to grow on two of the medium: one containing a radioactive isotope of phosphorus( 32 P) and the other containing a radioactive isotope of sulfur ( 35 S).
• Phages grown on radioactive phosphorus( 32 P) contained radioactive P labeled DNA (not radioactive protein) as DNA contains phosphorus but not sulfur.
• Similarly, the viruses grown in the medium containing radioactive sulfur ( 35 S) contained radioactive 35 S labeled protein (but not radioactive DNA) because sulfur is found in many proteins but is absent from DNA.
• E. coli were introduced to be infected by the radioactive phages.
• After the progression of infection, the blender was used to remove the remains of phage and phage parts from the outside of the bacteria, followed by centrifugation in order to separate the bacteria from the phage debris.
• Centrifugation results in the settling down of heavier particles like bacteria in the form of pellet while those light particles such as medium, phage, and phage parts, etc., float near the top of the tube, called supernatant.

Observation of Hershey and Chase Experiment

On measuring radioactivity in the pellet and supernatant in both media, 32 P was found in large amount in the pellet while 35 S in the supernatant that is pellet contained radioactively P labeled infected bacterial cells and supernatant was enriched with radioactively S labeled phage and phage parts.

Conclusion of Hershey and Chase Experiment

Hershey and Chase deduced that it was DNA, not protein which got injected into host cells, and thus, DNA is the hereditary material that is passed from virus to bacteria.

• Fry, M. (2016). Landmark Experiments in Molecular Biology. Academic Press.
• https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Introductory_Biology_(CK-12)/04%3A_Molecular_Biology/4.02%3A_DNA_the_Genetic_Material
• https://byjus.com/biology/dna-genetic-material/
• https://bio.libretexts.org/Bookshelves/Genetics/Book%3A_Online_Open_Genetics_(Nickle_and_Barrette-Ng)/01%3A_Overview_DNA_and_Genes/1.02%3A_DNA_is_the_Genetic_Material
• https://www.toppr.com/guides/biology/the-molecular-basis-of-inheritance/the-genetic-material/
• https://www.nature.com/scitable/topicpage/discovery-of-dna-as-the-hereditary-material-340/
• https://www.biologydiscussion.com/genetics/dna-as-a-genetic-material-biology/56216
• https://www.nature.com/scitable/topicpage/discovery-of-the-function-of-dna-resulted-6494318/
• https://www.ndsu.edu/pubweb/~mcclean/plsc411/DNA%20replication%20sequencing%20revision%202017.pdf
• https://www.britannica.com/biography/Frederick-Griffith
• https://ib.bioninja.com.au/higher-level/topic-7-nucleic-acids/71-dna-structure-and-replic/dna-experiments.html
• https://biolearnspot.blogspot.com/2017/11/experiments-of-avery-macleod-and.html
• https://www.khanacademy.org/science/biology/dna-as-the-genetic-material/dna-discovery-and-structure/a/classic-experiments-dna-as-the-genetic-material

About Author

Prakriti Karki

Leave a Comment Cancel reply

Save my name, email, and website in this browser for the next time I comment.

This site uses Akismet to reduce spam. Learn how your comment data is processed .

Talk to our experts

1800-120-456-456

Hershey and Chase Experiment

Hershey and Chase Experiment: An Introduction

There were many scientists who knew that the element essential for inheritance is found within the body of an organism, but they failed to discover it. Many experiments were performed to extract the chromosomal components, but the question of inheritance remains unanswered. However, with the advent of Griffith’s experiments, the path was opened for the discovery of genetic material.

Working off on Griffith's experiment, Avery and his colleagues successfully isolated DNA and demonstrated that DNA is the genetic material. However, until Hershey and Chase published their experimental data, not everyone agreed with this theory.

The Hershey and Chase Experiment

Hershey and Chase Experiment Diagram

To establish that DNA serves as the genetic material, the Hershey-Chase experiment was carried out in 1952.

E. coli and the bacteriophage T 2 were used in the tests conducted by Hershey and Chase.

The bacteriophage binds to the bacteria and introduces its genetic material into the bacterial cell . It has DNA and a protein coat.

Some T 2 phages were cultivated in radioactive sulphur ( 35 S) media, while the other T 2 phages were cultured in a radioactive phosphorus ( 32 P) medium.

While the T 2 phages in ( 32 P) medium contained radioactive DNA because the protein coat does not contain phosphorus, the T 2 in ( 35 S) medium contained radioactive protein due to the absence of sulphur in the DNA.

After that, the radioactive phages joined the E. coli. As the illness grew worse, centrifugation was used to separate the viruses.

The fact that the radioactive DNA in the T 2 phage-infected E. coli was similarly radioactive suggests that DNA was the substance that was transferred from the virus to the bacteria.

Conclusion of Hershey and Chase Experiment: The bacteria that had been infected by the virus and coated with a radioactive protein coat were not radioactive, demonstrating that DNA is the genetic material transmitted from a virus to a bacteria.

Why is DNA Considered a Genetic Material?

It was discovered that DNA dominated the genetic makeup of the majority of species . There were notable exceptions, including certain viruses whose genetic makeup was RNA . But what distinguishes DNA from other molecules such as proteins , carbohydrates etc. as genetic material? Important requirements for being a genetic material are:

Able to replicate itself.

Structurally and chemically stable.

Give room for a mutation that could result in evolution .

Able to communicate itself with "Mendelian Characters".

The majority of other compounds, including proteins, carbohydrates and lipids , did not meet the aforementioned requirements. Although RNA could meet the requirements, DNA remained the favoured genetic material over RNA for the following reasons:

RNA is less stable structurally than DNA.

RNA is less stable chemically than DNA.

Due to its double-stranded structure, DNA can more easily correct replication faults.

RNA is required for protein synthesis because DNA can not code for it directly.

Pulse Chase Experiment

The Pulse-Chase Analysis is a technique used in Biochemistry and genetic experiments to look at the biological activity that is happening over time by exposing the cells to the same substance first in a labelled form (the pulse) and then in an unlabelled form (the second pulse) (chase).

This technique can be used to track a cell's activity over an extended period of time. Protein kinase C, ubiquitin and numerous other proteins have been studied using this technique. The technique was additionally employed to demonstrate the existence and utility of Okazaki fragments. To clarify the secretory process, George Palade used a pulse-chase of radioactive amino acids.

Alfred Hershey and Martha Chase carried out a series of tests in 1952 that helped to establish that DNA is the genetic material. These investigations are known as the Hershey-Chase experiments. Despite the fact that DNA has been known to biologists since 1869, many scientists at the time still believed that proteins contained genetic information because DNA seemed to be less complex than proteins.

In their tests, Hershey and Chase demonstrated that when bacteriophages , which are made up of DNA and protein, infect bacteria, only a small portion of their protein actually reaches the host bacterial cell. The prior, current and later discoveries all served to indicate that DNA is the hereditary material, even though the results were inconclusive and Hershey and Chase were circumspect in their interpretation. Max Delbruck, Salvador Luria and Hershey received the 1969 Nobel Prize in Physiology or Medicine for their discoveries relating to genetics.

FAQs on Hershey and Chase Experiment

1. What was Griffith's transforming principle?

Griffith was the one who initially conceived the idea of the transformative principle. The principle proved successful in converting a strain of non-pathogenic bacteria into a strain of pathogenic bacteria. Hereditary material is distinguished by a number of qualities, including the ability to undergo phenotypic change. Griffith referred to the component that was responsible for the altered phenotype as the transforming principle. It was determined through a series of studies carried out by Avery, McCartys and MacLeod that the hereditary material in question was DNA.

2. What is the semi-conservative DNA replication model?

The "semi-conservative DNA replication" model was proposed by Watson and Crick. The two DNA strands split apart in accordance with this theory. For the synthesis of a new strand, each strand serves as a template. Based on complementary base pairing with the template, the new strand is created. One parent strand and one freshly produced strand make up each new DNA molecule. This is how the single copy of the original DNA molecule is divided into two copies.

3. What is the biochemical nature of the transforming principle?

To find the transforming principle, bacteriologists did a number of experiments.

Alcohol precipitated the transforming principle. This demonstrated that it wasn't a carbohydrate.

Proteases were unable to eliminate the transforming principle. So, the protein was not the cause.

The lipases were unable to remove the transforming principle. This demonstrated that it wasn't a lipid.

Ribonuclease could not inactivate the transforming principle, hence RNA was not effective.

Deoxyribonuclease may be used to inactivate the transforming principle.

DNA was the transforming principle. As a result, DNA was the genetic material.

• Biotechnology
• Biochemistry
• Microbiology
• Cell Biology
• Cell Signaling
• Diversity in Life Form
• Molecular Biology

DNA as Genetic Material - Hershey And Chase Experiment

The Hershey and Chase Experiment , conducted in 1952 by Alfred Hershey and Martha Chase, demonstrated that DNA contains genetic information. They accomplished this by investigating viruses that infect bacteria, known as bacteriophages. In these tests, scientists labelled the virus's DNA with a radioactive marker while labelling the protein coat independently with another marker.

When the viruses infected bacteria, researchers discovered that only the DNA identifier, not the protein marker, was passed along to the next generation of viruses. This helped to demonstrate that DNA, not protein, is the molecule that conveys genetic instructions. We will read about the Hershey and Chase Experiment in detail in this article.

Table of Content

Hershey and Chase Experiment

Dna as genetic material, what is the pulse and chase experiment, conclusion -dna as genetic material: hershey and chase experiment.

• FAQs on DNA As Genetic Material - Hershey And Chase Experiment

In 1952, Alfred Hershey and Martha Chase investigated bacteriophage, a virus that destroys bacteria . Their research focused on T2 bacteriophage that infects the bacterium Escherichia coli (E. coli). Their goal was to determine whether the T2 phage's genetic instructions or information required for life, were stored in its DNA or protein coat. They wanted to show that the DNA, not the protein , contained this important genetic information.

There were three steps in the experiment:

• Centrifugation

Alfred Hershey and Martha Chase used two forms of radioactive material, phosphorus-32 (32P) and sulfur-35 (35S), to designate the bacteriophages differently. Phosphorus is a component of DNA, the genetic material, whereas sulphur is present in proteins but not DNA.

They inserted these radioactive isotopes into the bacteriophages DNA (genetic material) and protein coat (capsid) separately. This enabled them to determine which parts of the virus entered the bacterial cell during infection. They then allowed the labelled viruses to infect E. coli bacterial cells.

Following a brief time of infection, they mixed the liquid to separate the viral protein coatings from the bacteria. This blending phase ensured that any viral proteins that were not bound to bacterial cells were eliminated. They next centrifuged the mixture, causing the heavier bacterial cells to sink at the bottom of the tube while the lighter viral protein coatings (if present) remained in the liquid above, known as the supernatant.

The results demonstrated that bacterial cells infected with phages labelled with phosphorus-32 (32P) exhibited radioactivity. This suggested that the phages' DNA entered the cells during infection. In contrast, bacterial cells infected with phages labelled with sulfur-35 (35S) exhibited little to no radioactivity, indicating that the phages' protein coat (also known as capsid) did not enter the cells.

Based on these findings, Hershey and Chase concluded that DNA, rather than protein, serves as the genetic material transmitting bacteriophages' hereditary information. This experiment offered solid proof that DNA is the chemical responsible for conveying genetic information in living beings.

Scientists discovered that DNA is the primary factor in defining the characteristics of most living organisms . However, some viruses use RNA instead. So, for something to be genetic material, it must:

• Be able to create clones of itself (self replicable).
• Be stable structurally and chemicaly.
• Allow for mutations, which can lead to evolution.
• Be able to pass on traits according to Mendel's inheritance principles.

Most other compounds, such as proteins, carbohydrates , and lipids, did not meet the previously listed criteria. While RNA could meet those requirements, DNA was favoured over RNA for genetic material for a number of reasons:

• DNA has more structural stability than RNA.
• DNA has higher chemical stability than RNA.
• DNA has a double-stranded structure that allows it to effectively repair replication faults.
• RNA is required for protein production because DNA cannot directly code for them.

Approximate content of DNA in few organisms is given below:

Pulse-Chase Analysis is similar to a time-lapse camera for investigating what happens inside cells . In this procedure, cells are first exposed to a labelled chemical (the "pulse") that identifies certain molecules. Then they are given an unlabeled chemical (the "chase") to observe what occurs. This allows scientists to track how molecules migrate and change over time.

Researchers have utilised this method to analyse a variety of proteins, including protein kinase C and ubiquitin, as well as to better understand processes such as Okazaki fragment production during DNA replication. For example, George Palade used pulse-chase with radioactive amino acids to study how cells release chemicals.

Alfred Hershey and Martha Chase conducted to confirm DNA as the genetic substance. The Hershey-Chase investigations was crucial then as at that time many scientists believed that proteins contained genetic information rather than DNA. Hershey and Chase discovered that when viruses called bacteriophages infect bacteria, a small amount of their protein enters the bacterial cell. This suggested that DNA, not protein, was responsible for carrying genetic instructions. These findings, coupled with previous and subsequent discoveries, strongly showed that DNA was the genetic material. Later they received the Nobel Prize in Physiology or Medicine for their contributions to genetics.

Also Read: Search For Genetic Material – Molecular Basis Of Inheritance DNA Replication Difference Between Gene and DNA

FAQs on DNA as Genetic Material - Hershey And Chase Experiment

What are the 3 steps of hershey and chase experiment.

Hershey and Chase carried their experiment in three steps : infection, blending, centrifugation.

What was the Hershey and Chase Experiment Class 12?

The Hershey and Chase experiment, conducted in 1952 by Martha Chase and Alfred Hershey, demonstrated that DNA, rather than protein, is the genetic material of viruses. They used bacteriophages to track the transmission of genetic information.

How did the Hershey and Chase Experiment Work?

In the experiment, bacteriophages were labeled with radioactive isotopes: sulfur-35 for proteins and phosphorus-32 for DNA. The phages were allowed to infect bacterial cells. After infection, the phage protein coats were removed by agitating the mixture in a blender, separating them from the bacterial cells.

What is the Principle of Hershey and Chase Experiment?

Hershey and Chase experiment proving DNA as the genetic material was based on the principle Transduction which is the process by which DNA is transferred from one bacterium to another by a virus.

Why was the Hershey and Chase Experiment Significant?

The Hershey and Chase experiment provided crucial evidence supporting the idea that DNA carries genetic information. This discovery was instrumental in shaping our understanding of genetics and laid the foundation for subsequent research in molecular biology, including the elucidation of the structure of DNA by Watson and Crick.

Is DNA the only Genetic Material?

There are three types of genetic materials: DNA, RNA, and genes.

Why was E.coli used in Hershey and Chase Experiment?

E. coli was used in the Hershey and Chase Experiment because it is easily grown and reproduces quickly, making it ideal for genetic research.

What Virus did Chase and Hershey Study?

Chase and Hershey studied the T2 bacteriophage virus in their experiment.

What was the Radioactive in the Hershey and Chase Experiment?

They used radioactive sulfur (S35) to label protein and radioactive phosphorus (P32) to label DNA.

What was the Conclusion of Hershey and Chase Experiment?

The conclusion of Hershey and Chase experiment was that DNA and not protein is the genetic material passed from viruses to bacteria.

How did Hershey and Chase Modify the Virus?

Hershey and Chase modified the virus by labeling its DNA with radioactive phosphorus to track its transmission into bacterial cells.

Similar Reads

• DNA as Genetic Material - Hershey And Chase Experiment The Hershey and Chase Experiment, conducted in 1952 by Alfred Hershey and Martha Chase, demonstrated that DNA contains genetic information. They accomplished this by investigating viruses that infect bacteria, known as bacteriophages. In these tests, scientists labelled the virus's DNA with a radioa 7 min read
• Griffith Experiment - Transformation in Bacteria, DNA as Genetic Material Griffith's Experiment in 1928 demonstrated bacterial transformation, where non-virulent bacteria turned virulent upon exposure to heat-killed virulent strains. Avery, MacLeod, and McCarty experiment later confirmed in 1944 that DNA, not proteins, was the genetic material responsible for this transfo 8 min read
• Davisson-Germer Experiment Davisson Germer Experiment established the wave nature of electrons and validated the de Broglie equation for the first time. De Broglie proposed the dual nature of the matter in 1924, but it wasn't until later that Davisson and Germer's experiment confirmed the findings. The findings provided the f 8 min read
• How do the Traits and Characters get expressed? The most fundamental and important aspects of biology are heredity and evolution, which are connected by inheritable features. These two terminologies assist us in learning and comprehending how the life cycle on Earth continues. Both concepts are tied to one another, and there can be no evolution w 8 min read
• Rutherford's Alpha Scattering Experiment Rutherford's Alpha Scattering Experiment is the fundamental experiment done by Earnest Rutherford's Alpha Scattering Experiment that gives the fundamental about the structure of the atom. Rutherford in his experiment directed high-energy streams of α-particles from a radioactive source at a thin she 6 min read
• Genetic Diversity| Class 11 Geography Notes Genetic diversity alludes to the inconstancy in qualities inside a species, impacted by variables like change, hereditary float, and quality stream. It is significant for species survival because it empowers adjustment to change situations and the improvement of special characteristics. Preservation 7 min read
• Incomplete Dominance & Mendel's Experiment Incomplete Dominance is a form of intermediate inheritance where neither of the two alleles for a particular trait is completely dominant over the other. In this type of dominance, the heterozygous phenotype is a blend or intermediate between the two homozygous phenotypes. The concept of incomplete 6 min read
• Genetic Code and Mutations Genetic code and mutations are important to understand and explain the central dogma of biology. The set of rules governing how DNA sequences are translated into proteins is the genetic code. The four nucleotide bases adenine (A), thymine (T), guanine (G), and cytosine (C), which are organized in pa 5 min read
• ​Cytogenetics - Meaning, History, Techniques, and Application Cytogenetics is the branch of genetics that studies the structure, function, and behaviour of chromosomes. It involves techniques such as karyotyping, FISH, and CGH to detect chromosomal abnormalities. This field plays a crucial role in diagnosing genetic disorders, cancers, and prenatal conditions. 11 min read
• Urey-Miller Experiment -Diagram The Miller-Urey Experiment diagram explains the set-up of this experiment conducted in 1952 by chemists Stanley Miller and Harold Urey. This Miller-Urey experiments aimed to simulate the conditions of early Earth's atmosphere and oceans to investigate the possibility of abiogenesis, or the spontaneo 4 min read
• What Causes Genetic Disorders? Genetic Disorders occur when the gene of an organism faces some type of abnormality. There are many genetic disorders we can see including sickle cell anemia, down syndrome, colon cancer, Fabry disease, fragile X syndrome, and cystic fibrosis. There's no way to completely prevent genetic disorders, 2 min read
• Biotechnology And Its Application- Gene Therapy BiotechnologyBiotechnology is focused on the large-scale production of biopharmaceuticals, including microorganisms, fungi, plants, and animals that have undergone genetic modification. Its applications include the fields of medicine and diagnostics as well as food processing, GM crops for agricultu 10 min read
• Linkage And Recombination - Principles Of Inheritance And Variation Class 12 NCERT CBSE Class 12- Principles Of Inheritance And Variation- Linkage And Recombination: Linkage and recombination are the phenomena that describe the inheritance of genes. Linkage and Recombination both are related to the genetic information inherited from parents to offspring. Linkage is the tendency of 6 min read
• Principles of Inheritance and Variation CBSE Notes for Chapter 4 Inheritance is the term given to the process by which characters are passed from parents to offspring which forms the basis of heredity. Heredity is the process of passing down genetic traits from parents to offspring. The degree of difference in characters between a parent and offspring is called v 15 min read
• Genetic Code - Molecular Basis of Inheritance CBSE Class12- Molecular Basis Of Inheritance- Genetic Code: The sequence of nucleotides in deoxyribonucleic acid and ribonucleic acid which determines the amino acids sequence of proteins is known as Genetic code. DNA consists of information for protein sequences. RNA consists of four nucleotides: a 5 min read
• Difference Between Phenotype and Genotype Ratio Understanding the difference between phenotype and genotype ratio is essential in genetics. While phenotype refers to observable traits influenced by genotype, genotype represents the genetic makeup of an organism. Unraveling this distinction sheds light on inheritance patterns and genetic variabili 5 min read
• Difference between YAC and BAC Vectors The Difference between YAC and BAC Vectors is in their insert size, stability, host organism, and versatility. YAC vectors are good at holding large pieces of DNA, ranging from 100-3000 kbp base pairs. On the other hand, BAC vectors can hold smaller pieces of DNA, typically ranging from 150-350 kbp 8 min read
• Difference Between Euchromatin And Heterochromatin Difference Between Euchromatin And Heterochromatin: Euchromatin has a loose structure and high transcriptional activity while heterochromatin is quite dense and has low activity. Euchromatin contains genes and replicates first, while heterochromatin is involved in the regulation of chromosome struct 5 min read
• Genetic Algorithms and Genetic Programming for Advanced Problem Solving Genetic algorithms (GAs) and genetic programming (GP) are branches of evolutionary computing, a subset of artificial intelligence where solutions evolve over time to fit a given set of parameters or solve specific problems. These techniques are inspired by the biological concepts of reproduction, mu 7 min read
• School Biology
• School Learning

Improve your Coding Skills with Practice

What kind of Experience do you want to share?

Hershey and Chase Experiment

Hershey and Chase experiment give practical evidence in the year 1952 of DNA as genetic material using radioactive bacteriophage . Griffith also explained the transformation in bacteria and concluded that the protein factor imparts virulence to the rough strain, but it was not proved to be genetic material.

Avery , Macleod and McCarthy further studied the Griffith experiment and concluded that the DNA was the genetic material responsible for transforming the avirulent rough strain to the virulent strain. To resolve the query of genetic material, many researchers were engaged to know whether the cause of inheritance is protein or DNA.

Many assessments then led to the discovery of “ DNA ” as genetic material or the cause of inheritance . One of the best experiments that provide DNA evidence as genetic material is the “ Hershey and Chase experiment ”. We will study the definition, steps (radioactive labelling, infection, blending and centrifugation) and observation of the Hershey and Chase experiment in this context.

Content: Hershey and Chase Experiment

Radioactive labelling of bacteriophage, centrifugation, observation, definition of hershey and chase experiment.

Hershey and Chase’s experiment has demonstrated the DNA is the genetic material where they have taken the radioactive T2-bacteriophage (Viruses that infect E.coli bacteria). T2-bacteriophage or Enterobacteria phage T2 belongs to the Group-I bacteriophage.

Video: Hershey and Chase Experiment

Hershey and Chase Experiment Steps

Hershey and Chase gave full evidence of the DNA being a genetic material by their experiments. To perform the experiment, Hershey and Chase have taken T-2 bacteriophages (invaders of E.coli bacteria). The experiment includes the following steps:

Hershey and Chase have grown T-2 bacteriophages in the two batches. In batch-1, we need to grow the bacteriophages in the medium containing radioactive sulphur (S 35 ) and radioactive phosphorus (P 32 )  in batch-2. After incubation, we could see that the radioactive sulphur (S 35 ) will tag the phage protein. The radioactive phosphorus (P 32 ) will tag the phage DNA.

After radioactive labelling of the phage DNA and protein, Hershey and Chase infected the bacteria, i.e. E.coli by using the radioactively labelled T-2 phage. In batch-1, T-2 phage tagged with S 35 and in batch-2 T-2 phage labelled with P 32 were allowed to infect the bacterial cells of E.coli .

After the attachment of  T-2 bacteriophage to the E.coli , the phage DNA will enter the cytoplasm of E.coli . The phage DNA will take up the host cell machinery. Degradation of the bacterial genome occurs by the T2-phages where they use the ribosomes to form structural proteins of the capsid, tail fibres, base plate etc.

At the time of blending or agitation, the bacterial cells are agitated to remove the viral coats . As a result of the agitation, we get a solution containing bacterial cells and viral particles like capsid, tail fibres, base plate, DNA etc.

After the centrifugation, we could observe the results to identify the heritable factor . The phage DNA labelled with P 32  will transfer the radioactivity in the host cell. Thus, the radioactive P 32  enters a bacterial cell and exists in the form of “Pellets”. The phage protein tagged with S 35 will not transfer its radioactivity in the host cell. As a result, radioactive S 35 will appear in the form of  “Supernatant” in the solution.

The P 32 labelled phage DNA will transfer its radioactivity to the host cell DNA, while S 35 labelled phage protein will not do so. The P 32 labelled phage DNA will remain inside the E.coli cell even after blending and centrifugation. According to the Hershey and Chase experiment, we can conclude that the DNA is the genetic material because the P 32 tagged T2-phage DNA will transfer the radioactivity to the host cell ( E.coli ) not the S 35 labelled T2-phage protein.

Related Topics:

• Citrus Canker Disease
• Microbial Food Spoilage
• Acetic Acid Production
• Activated Sludge Treatment

Leave a Comment Cancel Reply

Your email address will not be published. Required fields are marked *

Start typing and press enter to search

Scan to visit

• Introduction to Genomics
• Educational Resources
• Policy Issues in Genomics
• The Human Genome Project
• Funding Opportunities
• Funded Programs & Projects
• Division and Program Directors
• Scientific Program Analysts
• Contacts by Research Area
• News & Events
• Research Areas
• Research Investigators
• Research Projects
• Clinical Research
• Data Tools & Resources
• Genomics & Medicine
• Family Health History
• For Patients & Families
• For Health Professionals
• Jobs at NHGRI
• Training at NHGRI
• Funding for Research Training
• Professional Development Programs
• NHGRI Culture
• Social Media
• Broadcast Media
• Image Gallery
• Press Resources
• Organization
• NHGRI Director
• Mission and Vision
• Policies and Guidance
• Institute Advisors
• Strategic Vision
• Leadership Initiatives
• Diversity, Equity, and Inclusion
• Partner with NHGRI
• Staff Search

1952: Genes are Made of DNA

Their experiment provided strong support for the idea that genes are made of DNA. They firmly restated the conclusion that Avery, et al. had more tentatively proposed in 1944.

Electron microscope images showed that a bacterial virus - bacteriophage T4 - attaches to a bacterium to infect it. Hershey and Chase figured that the virus transferred genetic material into the bacterium to direct the production of more virus.

They knew that bacteriophage T4 was made of protein and DNA. They also knew that proteins contain sulfur atoms but no phosphorus, while DNA contains a great deal of phosphorus and no sulfur. They used radioactive sulfur and phosphorus to label and, so, distinguish viral proteins from viral DNA. After allowing labeled viruses to infect bacteria, they observed that the radioactive phosphorus enters the bacteria while the radioactive sulfur always remains outside.

More Information

Hershey, A.D., Chase M., 1952. Independent functions of viral protein and nucleic acid in growth of bacteriophage. J. Gen. Physiol, 36:39-56. 1952. [ PubMed ]

« Previous Event | Next Event »

Last updated: April 23, 2013

• Biology Article
• Dna Genetic Material

DNA As Genetic Material - Hershey And Chase Experiment

Even though researchers discovered that the factor responsible for the inheritance of traits comes from within the organisms; they failed to identify the hereditary material. The chromosomal components were isolated but the material which is responsible for inheritance remained unanswered. Griffith’s experiment was a stepping stone for the discovery of genetic material. It took a long time for the acceptance of DNA as genetic material. Let’s go through the discovery of DNA as genetic material.

Experiments of Hershey and Chase

We know about Griffith’s experiment and experiments that followed to discover the hereditary material in organisms. Based on Griffith’s experiment, Avery and his team isolated DNA and proved DNA to be the genetic material. But it was not accepted by all until Hershey and Chase published their experimental results.

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.

The virus doesn’t have their own mechanism of reproduction but they depend on a host for the same. Once they attach to the host cell, their genetic material is transferred to the host. Here in case of bacteriophages, bacteria are their host. The infected bacteria are manipulated by the bacteriophages such that bacterial cells start to replicate the viral genetic material. Hershey and Chase conducted an experiment to discover whether it was protein or DNA that acted as the genetic material that entered the bacteria.

DNA as Genetic Material

Experiment: The experiment began with the culturing of viruses in two types of medium. One set of viruses (A) was cultured in a medium of radioactive phosphorus whereas another set (B) was cultured in a medium of radioactive sulfur. They observed that the first set of viruses (A) consisted of radioactive DNA but not radioactive proteins . This is because DNA is a phosphorus-based compound while protein is not. The latter set of viruses (B) consisted of radioactive protein but not radioactive DNA.

The host for infection was E.coli bacteria. The viruses were allowed to infect bacteria by removing the viral coats through a number of blending and centrifugation.

Observation:  E.coli bacteria which were infected by radioactive DNA viruses (A) were radioactive but the ones that were infected by radioactive protein viruses (B) were non-radioactive.

Conclusion: Resultant radioactive and non-radioactive bacteria infer that the viruses that had radioactive DNA transferred their DNA to the bacteria but viruses that had radioactive protein didn’t get transferred to the bacteria. Hence, DNA is the genetic material and not the protein.

For more video lessons on DNA as genetic material, visit  BYJU’S.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

Visit BYJU’S for all Biology related queries and study materials

Your result is as below

Request OTP on Voice Call

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Post My Comment

Byju’s is best

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.