The Discovery of DNA
It is amazing how important things are being discovered by persons who spend most of their lives dedicated to research. It is perhaps more amazing how a scientist discovers one thing while trying to discover other things. Imagine if no one was patient enough to conduct experiments to prove their assumptions. If that was the case, we would not know today that DNA is the genetic material. This paper will discuss how DNA was discovered, its structure and the scientists who contributed to the discovery.
Deoxyribonucleic acid (DNA) is considered as the molecular blueprint of life that can be passed to the next generation. It was discovered in 1953 (University of Georgia, 2007) from experiments seeking to understand bacterial pneumonia which claimed many lives during the twentieth century. During these experiments, researchers stumbled into discoveries which later on became the reagents for further experiments leading to the discovery of DNA as the genetic material (O’Connor, 2008).
DNA looks like a twisted ladder wherein rungs are secured by two out of four molecules that are interlocking. These molecules are nucleic acid bases. The four molecules include thymine, adenine, cytosine, and guanine (University of Georgia, 2007). Certain scientists have been notable for conducting experiments leading to the discovery of DNA. One of these was Oswald Avery whose team was trying to find out how to treat lobular pneumonia. From his experiments, he proved that DNA indeed carries genetic information.
During that time, many people believed that the gene would be made up of protein and not nucleic acid (WGBH, 1998). Another scientist which contributed to DNA discovery was Frederick Griffith who, in 1928, conducted an experiment utilizing pneumonia bacteria and mice. Recent studies pointed that Griffith’s experiment was one of many others hinting that DNA was the hereditary material. Griffith assumed from his experiment, wherein he used a smooth (S) and rough (R) strains of Streptococcus pneumoniae on a mice, that polysaccharide coating was the cause of the illness to the mice.
Further into his experiment, he found out that something in the living cell, and not the polysaccharides, caused the disease. Later on he speculated that the R strain bacteria he injected into the mice has absorbed the dead S strain bacteria’s genetic material. Furthermore, he speculated that the protein contained in the chromosomes was not the genetic bacteria due to the finding that heat denatures protein (Biology at Clermont College, n. d. ). At first, Avery was skeptical of the results of Griffith’s experiment. However, other researchers further studied Griffith’s findings.
In 1931, Sia and Dawson found out that transformation, a process wherein one strain absorbs the genetic material of another strain and becomes that bacterium, could also take place in liquid cultures of pneumococci and mice. In 1948, Linus Pauling found out that proteins are shaped in alpha helix, which looks like a spring coil. Another significant discovery took place two years later, when Erwin Chargaff discovered an important foundation of the description of DNA: nitrogen bases in DNA varied, but some bases occur in one-to-one ratio.
Pauling’s findings have further aroused interest into two researchers, namely: Francis Crick and James Watson. They were not the only ones interested in studying DNA. Maurice Wilkins and Rosalind Franklin from London were also studying DNA. Franklin discovered the possibility that DNA can occur in two forms. It depends on the humidity of the air. Franklin figured out that the molecule’s phosphate was located on the outside. Watson and Crick, determined to redeem their studies after a failed model, conceptualized that there are two chains of nucleotides in the molecule.
These two chains were in a helix, as what Franklin has discovered, but one chain was moving to the opposite direction of another. Furthermore, they believed that the strands of DNA molecule served as the template for the other. The strands separate during cell division. In addition, a new half is built on each strand. The team found out that this was the way DNA reproduces without change in its structure (WGBH, 1998). The discovery of DNA was considered as the most important biological work and it has paved the way for further experiments and studies. Crick and Watson won the Nobel Prize for their findings.
Biology at Clermont College. (n.d). DNA structure and function. Retrieved January 30, 2009, from http://biology.clc.uc.edu/courses/bio104/dna.htm
O’Connor, C. (2008). Discovery of DNA as the hereditary material using Streptococcus pneumoniae. Nature Education, 1(1).
University of Georgia. (2007). Study suggests how DNA building block might have formed. Retrieved January 30, 2009, from http://www.world-science.net/othernews/071102_adenine.htm
WGBH. (1998). Watson and Crick describe structure of DNA. Retrieved January 30, 2009, from http://www.pbs.org/wgbh/aso/databank/entries/do53dn.html