Search For Genetic Material

The search for genetic material has been important in understanding inheritance and evolution. Scientists have explored various models and experiments to identify the substance responsible for transmitting hereditary traits. From Griffith’s transformation experiments to Avery, MacLeod, and McCarty’s confirmation of DNA’s role, these discoveries have shaped modern genetics. This article delves into key experiments and milestones in the quest to unravel genetic material’s identity and significance in biological processes.

Understanding genetic material is crucial in Class 12 to grasp genetics and its properties comprehensively.

Many scientists performed various experiments to have evidence that determines that DNA is the genetic material. Previous discoveries made by Gregor Mendel, Walter Sutton, Thomas Hunt Morgan, and other scientists had narrowed the search to the chromosomes which are located in the nucleus of most cells but still the question of what molecule was actually the genetic material arises. Therefore the following experiments below determine the DNA as genetic material.

A couple of experiments were performed with Streptococcus pneumoniae by Frederick Griffith in 1928. When on a culture plate Streptococcus pneumoniae are grown some of them produce smooth shiny colonies (S) while others produce rough colonies (R). The mice die from pneumonia which is infected with the S strain (virulent) while the other does not develop pneumonia which is infected with the R strain.

• S Strain – Inject into mice – Mice die
• R Strain – Inject into mice – Mice live

Griffith was able to kill the bacteria by heating them. When the heat-killed S strain bacteria were injected into the mice, it doesn’t kill the mice while when the heat-killed S strain and live R strain bacteria the mice died. Therefore, he recovered the living S bacteria from the dead mice.

• S strain – Inject into mice – Mice live
• S strain + R strain – Inject into mice – Mice die

Lastly, Griffith concludes that R-strain bacteria were transformed by the heat-killed S-strain bacteria which happens due to the transfer of the genetic material But he cannot conclude about the biochemical nature of genetic material.

Oswald Avery, Colin Macleod, and Maclyn McCarty worked together to determine the biochemical nature of the transforming principle in Griffith’s experiment. They purified the biochemicals such as proteins, DNA, RNA, and so on from the heat-killed S cells to analyze which one could transform live R cells into S cells.

They discovered that DNA alone from the S bacteria causes R bacteria to become transformed. They also discovered that the transformation doesn’t affect the protein-digesting enzymes and RNA-digesting enzymes. Therefore it was concluded that transforming substances are not RNA or protein and DNA was the cause of transformation. Thus, DNA is the hereditary material.

• It should be stable both structurally and chemically.
• It should express itself in the form of Mendelian Characters.
• It should follow mutation for evolution.
• It should obey replication and therefore can able to replicate.

Replication of DNA

Replication of DNA is the process in which two strands separate and act like a template for the synthesis of new complementary strands. When replication is completed each DNA molecule consists of one parental and one new synthesis strand. The schema of replication was known as semiconservative DNA replication.

DNA (deoxyribonucleic acid) serves as the fundamental genetic material in all known living organisms. Its role was confirmed through landmark experiments such as the Avery-MacLeod-McCarty experiment in 1944, which demonstrated that DNA, and not protein, carries genetic information. Further studies, including the Hershey-Chase experiment in 1952, solidified DNA’s role by showing that viral DNA, not protein, directs viral replication.

These discoveries revolutionized biology, leading to the understanding that DNA encodes hereditary information through its sequence of nucleotides, which governs the development, function, and diversity of living organisms. DNA’s significance continues to underpin advancements in genetics, medicine, and biotechnology today.

To identify genetic material has been a journey marked by groundbreaking discoveries and experiments, culminating in the recognition of DNA as the molecule responsible for transmitting hereditary information. From the initial doubt to the conclusive experiments, scientific efforts have revolutionized our understanding of inheritance and paved the way for transformative advancements in genetics and biotechnology. DNA stands as the cornerstone of biological research and discovery.

What do you mean by the Transforming Principle?

It is a principle in which a couple of experiments were performed with Streptococcus pneumoniae by Frederick Griffith in 1928 to conclude the transfer of genetic material.

What has been Concluded from the Hershey and Chase Experiment?

It has been concluded that DNA was the material that passes from virus to the bacteria. The bacteria which were infected by the viruses had radioactive proteins and were not affected. Thus, it indicates that protein did not enter the bacteria from the viruses which proved that DNA passes from virus to bacteria and DNA is a genetic material.

What are the Two Properties of Genetic Material?

The two properties of Genetic material are as follows: It should follow mutation for evolution, and it can able to replicate.

What do you mean by Replication of DNA?

It is the process in which two strands separate and acts like a template for the synthesis of new complementary strands.

Who Discovered Genetic Material?

Alfred Hershey and Martha Chase conclusively demonstrated in 1952 that DNA serves as genetic material. Their groundbreaking experiments with bacteriophages provided compelling evidence supporting DNA’s role in heredity, establishing it as the primary molecule responsible for transmitting genetic information in living organisms.

What is Genetic Material Class 12?

Genetic material refers to molecules like DNA or RNA that carry genetic information and pass it from one generation to the next.