This essay examines the fundamental structure and biological function of deoxyribonucleic acid (DNA). Beginning with the historical discovery of the double helix by Watson and Crick in 1953, the paper explains how DNA's four nucleotide bases — adenine, thymine, guanine, and cytosine — pair to form a stable double-stranded molecule. It then traces the processes of DNA replication, transcription, and translation, describing how genetic information stored in base-pair sequences is converted into proteins within ribosomes. The essay concludes by connecting this molecular knowledge to modern biotechnology, including gene insertion techniques that allow scientists to modify living organisms.
DNA, or deoxyribonucleic acid, is the fundamental molecule upon which life on Earth is constructed. In a very real sense, DNA functions as a kind of program for life — one that cells use to replicate themselves and transmit information from generation to generation. Over eons, as life changes and adapts to new environmental conditions, that information is stored in the genetic code of all living organisms as DNA molecules evolve and are altered to meet those changing conditions. The result is the myriad different forms of life now present on the planet, a variety that is all the more remarkable because it is based on the same fundamental piece of biological software: DNA. Incredibly, DNA is a relatively simple chemical compound — so simple, in fact, that early researchers were dubious that it could be considered the molecule of life ("The Discovery of the Molecular Structure of DNA"). Nonetheless, despite its simplicity, DNA possesses a complex genetic code that contains all the instructions necessary for its own replication as well as the synthesis of proteins within living cells.
It is therefore crucial to our understanding of life on this planet that we understand the chemistry behind DNA. The interactions of the few basic chemicals that constitute DNA are responsible for all manifestations of life. Without straying too far into scientific reductionism, it is nonetheless apparent that a deeper understanding of the workings of DNA can provide new insights into the ways in which life arose and has developed over the past several billion years. Analysis of the chemistry of DNA is also relevant to furthering our understanding of the existing biological community and humanity's place within it. This essay examines some of the basic underpinnings of the structure and nature of DNA, including replication, protein synthesis, ribosomes, and the genetic code.
As early as the 1940s, scientists began to suspect that DNA was the basic molecule of life through which traits were passed from one generation to the next. What eluded them, however, was a clear understanding of the structure of the DNA molecule itself. The mysteries that would be resolved by many scientists — including Watson and Crick — included the fact that DNA was comprised of a "phosphate backbone on the outside with bases on the inside" and that the spatial organization of these components formed the double helix ("The Discovery of the Molecular Structure of DNA"). Though these chemical revelations seem simplistic and obvious today, at the time the scientific community lacked the understanding of genetic molecular mechanics necessary to grasp the basic chemical interactions of which DNA is a critical part.
When Watson and Crick published their seminal paper on the structure of DNA in 1953, they had resolved that structure based on their own and others' prior understanding of the DNA molecule. In addition to being a double helix, DNA is comprised of varying amounts of four bases: adenine, thymine, guanine, and cytosine. Importantly, Watson grasped the key concept that the amount of adenine in a given DNA molecule is always equal to the amount of thymine; the same is true of guanine and cytosine. Furthermore, the chemical bond between adenine and thymine is exactly the same length as the chemical bond between guanine and cytosine. That revelation meant that the double helix shape of the DNA molecule would take on a more elegant form, as each "rung" in the helix is equal in length, meaning the "sugar-phosphate backbone would be smooth" ("The Discovery of the Molecular Structure of DNA").
Specifically, DNA is composed of two chemical strands that run in opposite directions. On the outside of each strand is a sugar-phosphate backbone, with bases of adenine, thymine, guanine, and cytosine on the inside. The bases on the inside of the strands are always paired with bases on the complementary strand: adenine is always bonded to thymine via a two-hydrogen bond, and guanine to cytosine via a three-hydrogen bond. This pairing structure significantly restricts the arrangements that can be created with two separate strands of DNA — a fact that is of the utmost importance during replication ("The Discovery of the Molecular Structure of DNA").
When DNA is being copied, it is separated along the base pairs, which then form the foundation for a new helix. When one DNA helix is "unzipped" in this fashion, the result is the construction of two — ideally identical — strands of DNA. The copying of DNA into more DNA is known as replication and is the basis by which DNA is propagated and spread throughout living organisms. Replication begins with the local separation of DNA strands by a DNA polymerase enzyme, a process that allows the split halves to be available for enzymes within the cell that construct complementary copies from sugar-phosphates and bases present in the cell ("Replication/Transcription/Translation").
"How DNA copies itself via polymerase enzymes"
"RNA converts genetic code into cellular proteins"
"Biotechnology applications of molecular DNA knowledge"
You’re 52% through this paper. Sign up to read the remaining 3 sections.
Sign Up Now — Instant Access Already a member? Log inAlways verify citation format against your institution’s current style guide requirements.