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AVERY OSWALD (1877-1955)

Avery Oswald was a Canadian-born American physician who provided the molecular explanation for Griffith’s transformation of Streptococcus pneumoniae. Avery and his colleagues [Colin MacLeod (1909–1972) and Maclyn McCarty (1911–2005)] from the Rockefeller Institute were the first to publish evidence in the early 1940s that genes are actually made up of deoxyribonucleic acid (DNA) molecules. This was one of the most important discoveries of the 20th century because it paved the way for the genetic manipulations of living organisms, and also for understanding how genetic factors (particularly genes) direct the processes of reproduction, metabolism, pathogenesis and transformation in organisms including microbes. Avery was one of the first molecular biologists and a pioneer in immunochemistry and molecular biology. He is best known for his discovery in 1944 ‘that DNA is the material of which genes and chromosomes are made’.This discovery of his was made with his co-workers Colin MacLeod and Maclyn McCarty.


The principle of bacterial transformation was actually established by the works of Avery, MacLeod and McCarty and Frederick Griffith. They all showed that bacterial transformation could be carried out in the test tubes instead of the mouse that was previously used by Griffith in demonstrating this principle of bacterial transformation. Their painstaking experiment in deciphering this showed that DNA was actually the transforming agent or genetic material that makes up genes and chromosomes. The experiments of Avery and colleagues as well as those of Griffith established that DNA and not protein contained the genetic information of an organism. This discovery of theirs laid the foundation for the concept of the ‘central dogma of molecular biology’. The central dogma of molecular biology shows how genetic information contained in the DNA are transcribed to messenger ribonucleic acid (mRNA), and how it is later translated to the production of specific protein molecules that eventually carries out the work encoded in the DNA in the organism.


James Watson was born on the 6th of April, 1928, and he is an American molecular biologist, geneticist, and zoologist, who is best known as a co-discoverer of the structure of deoxyribonucleic acid (DNA) in 1953. Watson co-discovered the structure of the DNA with Francis Crick in 1953. Watson and Crick both published their model of the actual structure of the DNA, and this provided a theoretical frame work for how the DNA could serve as a genetic material. There discovery of the nucleic acid (i.e., DNA as the genetic material) was very significant because it showed the basic principles underlying the mode of transmission of genetic materials from one organism to another, especially from the parent cell to the daughter cell. Three types of studies summarized the actual structure of the DNA and they are:

  1. The bacteriological studies of Frederick Griffith.
  2. The biochemical studies of Oswald Avery.
  3. The structural studies of James Watson and Francis Crick.

These studies by Frederick Griffith, Oswald Avery, James Watson and Francis Crick summarized the actual structure of the DNA as the major genetic material of the cell, and this gave impetus to the rise of the field of molecular biology as well as the manipulation of the genome of living organisms including microbes for other beneficial purposes by man. The findings and discoveries of these notable scientists ‘about the DNA and its structure and importance or role’ helped to solidify the concept of DNA (deoxyribonucleic acid) as the major genetic material of the cell. The works of these scientists led to the development of the whole field of molecular biology and molecular genetics as well as recombinant DNA technology as we know it today; and this came as a result of the integration of the boundaries between the subjects Microbiology, Genetics and Biochemistry. The double helix of the DNA structure as we know it today was figured out by Watson and Crick; and this discovery has tremendously impacted and revolutionized the practice of medicine and biomedical sciences. The 1962 Nobel Prize in Physiology or Medicine was awarded to Watson and Crick because of their discovery of the molecular structure of the DNA.

Further reading

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of microorganisms. 12th edition. Pearson Benjamin Cummings Publishers. USA. Pp.795-796.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Prescott L.M., Harley J.P and Klein D.A (2005). Microbiology. 6th ed. McGraw Hill Publishers, USA. Pp. 296-299.

Singleton P and Sainsbury D (1995). Dictionary of microbiology and molecular biology, 3d ed. New York: John Wiley and Sons.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

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