DNA is The Basis of Life - Essay Example

DNA: The Basis of Life The question of “What is life, and what is it made of” has been asked to the point of making it cliche,if not ubiquitous, yet a multitude of answers persist. Life could be defined as a potential, as a response to external stimuli, or even as an indefinable feeling, yet none of these answers attempts to solve the question of what actually drives the biological engine of our bodies that keeps us breathing, pumping blood, and absorbing food. On April 25th, 1953, the now famous scientific pair of Watson and Crick attempted to finally answer this question (Fredholm). They claimed that an elegant molecule called deoxyribonucleic acid, or DNA, was the “God Molecule”, the blueprint for every protein in our body (and the subsequent molecules those proteins go on to make), the stuff of life (What Is DNA? - Genetics Home Reference). So what is this holy grail of biological molecules? This review will attempt to answer that question by covering the history of the discovery of the molecule, and its general structure and function. Because of its extraordinary properties, DNA forms the basis of life and of our bodies as we know them. The history of the discovery of DNA has the drama of a spy novel and an importance greater than nearly any scientific revelation before or after its discovery, yet credit for its discovery is mostly given to two major contributors. The real discovery of the field of genetics occurred in a small monastery where Austrian monk Gregor Mendel worked with his pea plants (Gregor Mendel). Mendel observed that some plants produced strange, abnormal features whereas other plants grew typically. Mendel took abnormal plants and crossed them with normal plants to observe the progeny. If the daughter plants from the two parents showed traces of the abnormality from one of the parents, Mendel could attribute the abnormality to something inherited between generations of plants. If, on the other hand, the plant did not show any traces of abnormality, Mendel could assume the environment caused the atypical features of the plant. Obviously, the daughters of the crossed plants showed traces of abnormality, and the field of genetics was started (Gregor Mendel), yet despite the brilliant work being done by Mendel, it would still be almost a century later until DNA was discovered. Years later when Watson and Crick decided to attempt to solve the great scientific puzzle of their era, several key facts still needed to be solved in order to develop a complete model of DNA, mainly, was it a double or triple helix and were base pairs pared on the inside or outside of the backbone (Fredholm)? In 1951, Watson and Crick thought they had the puzzle solved. They had completed a model of a triple helical model with base pairs extending out from a central phosphate backbone, a model very similar to one proposed by scientific legend Linus Pauling, yet this model was incorrect. At the same time, Rosalind Franklin was producing high quality x-ray crystallography pictures of DNA for Maurice Wilkins; pictures scientist JD Bernal called “the most beautiful X-Ray photographs of any substance ever taken.” (Rosalind Elsie Franklin: Pioneer Molecular Biologist) These pictures showed the actual structure of DNA, but required expertise in the interpretation of such pictures to be able to understand them. The pieces of the drama were in place; to solve the puzzle, Watson and Crick needed scientific evidence to support and complement their ball-and-stick modeling method, yet only one scientist had what they needed: Rosalind Franklin (Fredholm). Then, in a regretful moment, Franklin’s partner Wilkins showed Watson one of her DNA X-Ray pictures, the pieces snapped into place for Watson, and he and Crick would go on to publish the groundbreaking article revealing the structure of DNA, with Franklin’s and Wilkins’s work being listed as supporting works. The saddest part of the whole story is Franklin’s early death. Rosalind Franklin died in 1958, four years before Watson, Crick, and Wilkins would go on to each accept Nobel Prizes (Fredholm). Despite the lack of credit she was given at the time, Rosalind Franklin is viewed as a pioneer not only in the fields of genetics and women in science, but of the modern scientific era. Watson, Crick, Wilkins, and Franklin all realized that because of its extraordinary properties, DNA forms the basis of life and of our bodies as we know them. Equally contributing to the beauty of the molecule is its structure and function. As Watson and Crick reported, DNA is made of two parts: a “backbone” composed of a phosphate group and a sugar, and base pairs consisting the nucleotides adenine, guanine, cytosine, and thymine (What Is DNA? - Genetics Home Reference). Early scientific studies before the discovery of DNA occurred showed that adenine content of DNA is equal to thymine content, just as guanine content is equal to cytosine content. After the discovery of the structure of DNA, scientists realized that the reason for this is that the nucleotides adenine and thymine bind to form a base pair, just as guanine and cytosine do. On one side, the nucleotide will be bound to a phosphate backbone, on the other side, it will be bound to another nucleotide that is bound to a separate phosphate backbone. Phosphate backbones connect to each other vertically through bonds with the sugars of the backbone. As the base pairs of DNA bond and “zipper up” to form a complete molecule, an anti-parallel, double helical molecule with two phosphate sugar backbones surround a spiral of base pairs (What Is DNA? - Genetics Home Reference). As is so often the case in chemistry, this structure will go on to determine and alter the function of DNA. The structure of DNA determines the function of DNA because the structure of DNA encodes its function. One of the most revolutionary parts of the discovery of DNA’s structure was the discovery that DNA is composed of two complimentary strands; meaning the nucleotides connected to each of DNA’s two backbones are not replicas of each other, but complement each other. An adenine on one strand will match to a thymine on another strand in the exact same position. This shows that each strand essentially codes for the same information, just in complementary terms (Fredholm). Because of this, when DNA is read by cellular machinery, either strand can be read. Furthermore, cellular machinery reads the nucleotide code of either strand to determine what proteins to make for that cell. These proteins can be molecules as diverse as neurotransmitters, cellular gates, and even pieces of cellular organelles, yet they all share a common origin of information in DNA. In this way, DNA acts as the blueprint for every molecule our body creates. Furthermore, molecules that are not directly coded for by DNA, such as lipids and carbohydrates, are created in the body and in cells by proteins encoded for by DNA. This is why DNA can be said to be the blueprint for every living thing: because DNA codes for the proteins that compose every living thing, and these proteins go on to create or modify almost every biological molecule. Beyond its complimentary structure and universal function, DNA’s beauty lies also in its ability to store and protect itself, another function based on its structure. In humans, DNA stores itself as the 23 chromosomes everyone has heard of before, but how does DNA go from long strands to this chromosome form? By tightly wrapping itself around small proteins it codes for. These proteins are called histones, and their code is one of the most preserved across species and time in DNA (Histone Protein Structure). Histones are like small-scale DNA spools in that DNA winds itself around them to compact and protect itself. This process happens without energy input, and requires no energy to initiate, DNA simply conforms itself to these histones when it needs to be stored because of its structure. Just like a string that has been would repeatedly until the winds curl in on themselves, eventually these DNA-histone complexes form more compact structures that form even more compact structures until DNA has formed the chromosome we are so used to seeing (Histone Protein Structure). It is because of these extraordinary properties that DNA forms the basis of life and of our bodies as we know them. So in response to the question of “what is life, and what is it made of”, revolutionary thinkers like Mendel, Watson, Crick, Wilkins, and Franklin have contributed their answers. They say DNA is the stuff of life, and the reason we are even able to process this question, yet is this the final answer? Certainly DNA accounts for a great deal of the variability associated with a definition of life; if you consider life breathing, DNA makes this possible, if you consider life thinking, DNA makes this possible, and if you consider life happiness, DNA also makes this possible, yet clearly each of these things is not life itself. DNA makes biological life possible, but there is another aspect of life that is not accounted for by simply living and experiencing. This indefinable quality makes itself apparent when we step back and appreciate the true beauty of DNA: its universality, its elegant structure, and its superior memory all have the ability to inspire awe and wonder in humans, and it is this awe that adds further to the quality of the life DNA makes possible. Works Cited 1. Fredholm, Lotta. "The Discovery of the Molecular Structure of DNA - The Double Helix." Nobelprize.org. The Nobel Prize. Web. 06 June 2011. . 2. "Gregor Mendel." Zephyrus Interactive Education Website. Web. 06 June 2011. . 3. Histone Protein Structure." Memorial University. Web. 06 June 2011. 4. "Rosalind Elsie Franklin: Pioneer Molecular Biologist." San Diego Supercomputer Center. Web. 06 June 2011. . 5. "What Is DNA? - Genetics Home Reference." Genetics Home Reference. NIH. Web. 06 June 2011. . Read More