According to molecular biologists there are four major reasons why they are convinced that the DNA contains the genetic material and these reasons are listed below (Hawley & Mori, 1999): 1. the type of radiation that can cause mutation can be efficiently absorbed by the DNA than by other components of the cell; 2. bacteriologists were able to ascertain that when a virus infects a bacterial cell it is only the DNA of the virus that enters the cell of the bacteria while its protective covering made of protein is unable to enter and left outside the cell upon entry;
The amount of DNA in sex cells was precisely half of the amount of DNA found in other cells of the body and this consistent with the laws of inheritance espoused by Mendel; and finally 4. the experiments performed by Avery, Mcleod and McCarty was the final piece of evidence that enabled biologists to confirm that DNA is the genetic material. Every indication pointed to the DNA as the genetic material but as mentioned earlier it is hard to accept that it is indeed the means of replicating proteins, it is more logical to consider protein as the substance that guided the cells to manufacture fresh batch of proteins.
One has to be aware of the scientific environment during that time. For instance there was limited knowledge about the molecular structure of DNA. It was years later after Avery, Mcleod and McCarty’s breakthrough experiment that other scientists were able to fully understand the design and shape of the DNA molecule. By studying the structure it would be easier to understand why indeed the DNA is the genetic material. A Complex Structure There is a good reason why the genetic material is given an odd-sounding name.
This can be explained by simply looking at the structure of the DNA. It is called deoxyribonucleic acid because it a zipper-like molecule containing two separate chains that at same time are wrapped around each other and tightly coiled, allowing it to contain a great amount of information and yet function in the very tight confines of a cell’s nucleus (Hawley & Mori, 1999). It is truly amazing to imagine the ability of the cell to synthesize proteins using the code of life found in the DNA considering that it is tightly coiled and that there is very little room to maneuver.
The overall design can be likened to a spiral staircase and the two handrails correspond to the two chains while the step-like structure connects this two chains together (Hawley & Mori, 1999). It is known worldwide as a double-helix and yet words alone are not enough to describe its complexity. The step-like structures are called base pairs. The two chains on the other hand are made up of a repeating group of four different subunits called nucleotides. These nucleotides are base substances and these are: a) adenine (A); thymine (T); cytosine (C); and guanine (G).
The sugar molecules that link the bases are linked together by phosphates. This explains why the double helix structure can open up like a zipper and the information contained within can be understood, copied, transmitted and used as code to manufacture proteins. Conclusion The discovery of the DNA as the genetic material was one of the most important discoveries in the 20th century. Man is now closer to solving the mystery of life. From a scientific point of view, Avery, Mcleod and McCarty’s discovery paved the way for more scientific breakthroughs. For instance, it prompted Watson and Crick to find out the exact structure of the DNA.
Watson and Cricks discovery added another milestone in biology and this discovery pointed to another uncharted territory that must be explored. It is the works of Avery and his team and the discovery of the structure by Watson and Crick that enabled scientists to fully understand the DNA. While Mendel was only able to provide an overview of the laws of inheritance and a basic framework as to how parents’ genes can influence the physical characteristics of their still unborn child the discovery of the DNA molecule provided a way to understand the intricacies of genetics.
It is now more clear as to why microscopic cells can obtain the data necessary for replication of proteins and how this process is made possible in the narrow confines of the cell. The discovery of the genetic material and the subsequent discovery of its double helix structure not only paved the way for a clearer understanding of genetics but it also allowed health experts in the biomedical field to develop vaccines. It allowed biotechnologists to enhance farm production and it allowed others to dig a little deeper into the mystery of life and therefore added insights into life is perpetuated on earth.
These discoveries related to the DNA as the genetic material can help in the development of medicines that can finally defeat pathogens that are currently incurable. Although there are viruses that could not be contained by the human immune system and could not be prevented or treated with vaccines, the discovery of the DNA as the genetic material allows for a better chance in finding solutions to these problems. If not for Avery, Mcleod, and McCarty the scientific community and the rest of mankind would have still been groping in the dark in the attempt to understand life and the scientific basis for inheritance.
References
Alberts, B. et al. (1998). Essential Cell Biology. 2nd ed. New York: Garland Science. Hausmann, Rudolph. To Grasp the Essence of Life. MA: Kluwer Academic Publishers, 2002. Hawley, R. S. & C. A. Mori. (1999). The Human Genome. CA: Academic Press. Lacadena, J. R. “Cytogenetics: Yesterday, today and forever. A conceptual and historical overview. ” Chromosomes Today. Eds. Henriques-Gil, N. , J. S. Parker, & M. J. Puertas. New York: Springer, 1997, 3-10. Simmons, John. Doctors and Discoveries. MA: Houghton Mifflin Company, 2002.