Question

Name the scientists who proved experimentally that DNA is the genetic material? Describe their experiment.

Answer 1

DNA contains in the cells, and is deoxyribonucleic acid. It has been passed on from the parents to offspring and determines their traits. The finding that DNA is just the genetic material of molecular biology was also a significant landmark.

Complete answer:
First we should know about scientists who discover DNA to answer this question. Griffith and Hershey and Chase are the two researchers who proved that the genetic material is DNA.

-The Transition Experiment of Griffith:
In a series of experiments with Streptococcus pneumoniae (the bacterium known for pneumonia), Frederick Griffith observed a miraculous transformation of the bacteria in 1928.
Others develop smooth, glossy colonies (S) when Streptococcus pneumoniae (pneumococcus) bacteria are developed in a pure culture, while others develop rough colonies (R).
This is because there is a polysaccharide coat of the S strain bacteria, whereas there is no R strain. Mice affected with the S strain (virulent) die from infection with pneumonia, but pneumonia does not grow in treated mice with the R strain.

Mice infected with S strain - Mice die
Mice infected with R strain - Mice survive
Griffith was able to destroy bacteria through heating them. He found that they were not destroyed by heat-killed S strain bacteria inserted into mice.
Mice infected with heat killed S-strain- Mice survive
The mice died when he infused a blend of heat-killed S and live R bacteria.
Moreover, from the dead mice, he retrieved live S bacteria.
He assumed that the heat-killed S strain bacteria had somehow been changed by the R strain bacteria. >The R strain was able to synthesise a smooth mucous coat and become virulent by a certain 'transforming concept' converted from the heat-killed S strain. This must be as a result of the genetic material being passed.

Experiment on Hershey and Chase:
"DNA is the hereditary material" was the result of Alfred Hershey and Martha Chase's (1952) experiments. They were dealing with viruses called bacteriophages that infect bacteria.
The bacteriophage binds to the bacteria and then reaches the bacterial cell through its genetic material. The bacterial cell recognises the viral genetic material as if this is its own and creates more particles of the virus afterward. Hershey and Chase worked to figure out if the virus that entered the bacteria was protein or DNA.

Some of the viruses were grown on a medium containing radioactive phosphorus and others on a medium containing radioactive sulphur. Radioactive DNA was present in viruses grown in the presence of radioactive phosphorus, and not radioactive protein, since DNA absorbs phosphorus, but protein does not. Similarly, since DNA will not contain sulphur, viruses developed on radioactive sulphur include radioactive protein and not radioactive DNA.

It was permissible for radioactive phages to bind to E. Bacterium coli. Then the viral coats were erased from the bacteria as the infection initiated, by agitating them in a blender. By rotating them in a centrifuge, the virus particles are isolated from the bacteria.

Note: Radioactive bacteria were attacked by viruses that had radioactive DNA, meaning that the substance that transferred from the virus to the bacteria was DNA. Not nuclear were bacteria that were contaminated with viruses that had nuclear proteins. This means that proteins from the viruses did not reach the bacteria. Therefore, DNA contains information transmitted from viruses to bacteria.