DNA: Climbing the Ladder to new Heights of Exploration
When people think of exploration, they think of major geographical discoveries from explorers such as Ferdinand Magellan, Lewis and Clark, Edmund Hillary, or even Neil Armstrong, the first man to walk on the moon.
Although these explorations have changed the course of history, the term exploration does not have to refer only to geographical expansion. Scientific exploration has also led to important discoveries in the history of civilization. One major discovery came from two men who accidentally stumbled across the world’s biggest secret: the structure of Deoxyribonucleic Acid (DNA). The structure of DNA has cracked the code of the human genome which has provided critical insight into the base of human life. Although over 99% of the human genome is identical between individuals, a small number of sequential differences are used to distinguish all human beings.
The scientists who made this significant discovery were James Watson and Francis Crick. James Watson was born in Chicago, Ill., on April 6th, 1928. He received a scholarship to the University of Chicago at the young age of 15. In 1947, he received his B.Sc.
degree in Zoology. He became interested in the work of scientists at the University of Cambridge on photographic patterns made by X-rays so wrote his Ph.D. thesis on the effect of hard X-rays on bacteriophage multiplication. After he received his Ph.D.
in 1950, Watson spent time in Europe, first in Copenhagen and then at the Cavendish Laboratory of the University of Cambridge. Francis Crick was born on June 8th, 1916, in Northampton, England. He studied physics at University College, London, obtained a B.Sc. in 1937, and started research for a Ph.
D. In 1949 he joined the Medical Research Council Unit of which he has been a member ever since. He became a research student for the second time in 1950 when he was accepted as a member of Caius College, Cambridge. He obtained a Ph.D. in 1954 after writing his thesis entitled “X-ray diffraction: polypeptides and proteins”.
Prior to beginning his work with Watson, he worked out the general theory of X-ray diffraction by a helix, and suggested that the alpha-keratin pattern was due to alpha-helices coiled around each other. In 1951, Crick and Watson began working together at the Cavendish Laboratory and, along with another scientist, Maurice Wilkins, discovered the structure of the DNA molecule known as the double helix in March 1953. What brought about this discovery? Researchers working on DNA in the early 1950s used the term “gene” to mean the smallest unit of genetic information, but they did not know what a gene actually looked like structurally or chemically, or how it was copied, with very few errors, generation after generation. In 1944, Oswald Avery had shown that DNA was the carrier of hereditary information, in certain bacterium. Nevertheless, many scientists continued to believe that DNA had a structure too uniform and simple to store genetic information for making complex living organisms.
The genetic material, they reasoned, must consist of proteins which are much more diverse and molecules known to perform a multitude of biological functions in the cell. Crick and Watson recognized, at an early stage in their careers, that understanding the three-dimensional configuration of the gene was a central problem in molecular biology. Gaining knowledge in this field could lead to breakthroughs in genetics. They seized on this idea during their very first encounter. They pursued this information with a single-minded focus over the course of the next eighteen months. This meant taking on the task of immersing themselves in all the fields of science involved.
Because they conducted no DNA experiments of their own, they used the experimental results of others. They also took advantage of Crick’s scientific background in physics and X-ray crystallography and Watson’s knowledge of viral and bacterial genetics to show that DNA had a structure sufficiently complex and yet simple enough to be the master molecule of life. Although other researchers had previously made important but seemingly unconnected findings about the composition of DNA, most notably Rosalind Franklin, it fell to Watson and Crick to unify these findings into a coherent theory of genetic transfer. After several attempts at model building, they achieved their breakthrough. Jerry Donohue, a visiting physical chemist from the United States who shared Watson and Crick’s office for the year, pointed out that the configuration for the rings of carbon, nitrogen, hydrogen, and oxygen (the elements of all four bases) in thymine and guanine given in most textbooks of chemistry was incorrect. On February 28, 1953, Watson, acting on Donohue’s advice, put the two bases into their correct form in cardboard models by moving a hydrogen atom from a position where it bonded with oxygen to a neighboring position where it bonded with nitrogen.
While shifting around the cardboard cut-outs of the accurate molecules on his office table, Watson realized in a stroke of inspiration that the base pairs could be neatly fitted between the two helical sugar-phosphate backbones of DNA, the outside rails of the ladder. The bases connected to the two backbones at right angles while the backbones retained their regular shape as they wound around an axis, all of which were structural features demanded by the X-ray evidence. It was also proven that the backbones ran in opposite directions to each other, one up, and the other down. Watson and Crick published their findings in a one-page paper, with the title “A Structure for Deoxyribose Nucleic Acid,” in the British scientific magazine Nature on April 25, 1953, illustrated with a drawing of the double helix. Watson and Crick further expanded their ideas about genetic replication in a second article in Nature, published on May 30, 1953. The two had shown that in DNA, structure matches function: the double-stranded molecule could both produce exact copies of itself and carry genetic instructions.
The discovery of the DNA structure was the start of a new era in biology. There were technical advances too, such as DNA sequencing, genetic engineering, and gene cloning. More recently, the complete sequencing of many organisms has been solved- including the human genome in June of 2000. The next 50 years of the DNA story will be all about realizing the practical benefits of Crick and Watson’s discovery for humanity- in industry, medicine, food, and agriculture. One important area of DNA research is that of genetics and medical research.
Due to the discovery of DNA, our ability to diagnose diseases early on has been vastly improved. In addition, we have been able to better assess a person’s genetic predisposition to specific conditions. In doing so, we have also paved the pathway to formulate brand new drugs to treat these conditions. In fact, drugs can be custom made to complement a person’s personal biochemistry and genetic makeup. For diseases that were once considered lethal and where treatment was either non-existent or unsuccessful, the discovery of DNA has led to breakthrough drugs and treatments for patients.
In addition, experiments with DNA have impacted the way we identify and treat cancer. genetic testing has shown that some cancers can be predicted and treated early. DNA has been important to the field of forensic science. The discovery of DNA has meant that the guilt or innocence of a person who is charged with a crime may be determined. It also means that scarce evidence can still yield vital clues regarding the perpetrator of the crime.
Additionally, victims can be identified in cases where the victim’s condition is unrecognizable. In this sense, DNA has been important in revolutionising the entire field of forensic science. This impact is felt within the criminal justice system and helps to keep the public safe. The impact of DNA on agriculture is also significant because it has allowed farmers to facilitate the breeding of animals that have a better resistance to diseases. It also allows farmers to produce more nutritious produce, which has particularly important consequences in developing countries where the population subsists on a small range of staple foods.
This means that micronutrient deficiencies can be addressed in these countries. In 1962, Watson, Crick, along with Wilkins, shared the nobel prize in physiology for their discovery. Rosalind Franklin, who had contributed substantially to their research but passed away in 1958, was notoriously not included in this honor. Watson then wrote The Double Helix: A Personal Account of the Discovery of the Structure of DNA, which was published in 1968 and has never been out of print. James Watson retired from Cold Springs Laboratory and is currently living in Long Island, NY.
However, his colleague Francis Crick died in San Diego, CA, 2004 at the age of 88. . The double helix has not only reshaped the scientific world, but it has become a cultural icon represented in sculpture, visual arts, jewelry, and toys. Watson and Crick’s discovery has opened a world of vast new possibilities regarding medicine, criminal justice, and agriculture among other things. DNA has and will continue to shape the world we live in and will afford us countless new possibilities for exploration in the future.
