Abstract:
DNA (Deoxyribonucleic acid) is hereditary material found in most organisms and carries the genetic information required to build and maintain a living organism. DNA was first discovered in the late 1800's, but it was not until scientists unraveled its structure in the 1950s that its importance in genetics and the whole field of biological sciences became realized. This paper assesses the structure, history and applications of DNA into solving real world problems in medicine, agriculture, biochemical research and forensics. DNA can replicate itself which ensures that genetic information and consequently biological traits can be passed on from one generation to the next. The paper also covers information on the basic structure of DNA from the chemical bases and nucleotides and how all these are interconnected to create a double helix structure. The use of DNA information in protein synthesis is also explained briefly and finally the paper concludes by explaining the applications of DNA technology in modern science and industry.
Introduction:
Deoxyribonucleic acid (DNA) refers to the hereditary material found in almost all organisms and contains all the necessary genetic information needed to build and sustain an organism. DNA is thus the genetic blueprint of an organism since almost each cell in multicellular organisms has a full set of DNA. DNA specifies the structure and functioning of living organisms and serves as the primary heredity unit in organisms. For this reason, whenever organisms reproduce, a portion of their DNA is passed on to their offspring that ensures continuity from one generation to the next while at the same time allowing for slight alterations thus creating diversity. Most DNA is located in cell nuclei and is known as nuclear DNA, but it can also be found in the cell mitochondria, and in this case it is known as mitochondrial DNA (mtDNA) (Genome.gov, 2014).
DNA was first observed in the late 1800’s by a German biochemist known as Frederich Miescher, but it was not until a century later that researchers were able to unravel the structure of the DNA molecule and understand its importance (Genome.gov, 2014). In April 1953 Crick and Watson published a one page letter to the Nature magazine containing a model of the DNA helix. In fact, the letter had an understated message where they mentioned that the structure had been found to have “novel features which are of considerable biological interest” (Watson & Crick, 1953). Since then DNA has been used in various fields such as biochemical research, pharmacology, forensics and agriculture (Moulton, 2004).
In 1984, Alec Jefferies and his colleagues were able to develop genetic fingerprinting that used DNA to identify individuals. Other advancements include the first description of polymerase chain reaction (PCR) which was first described in the scientific literature in 1986 and served to help scientists to multiply small portions of DNA rapidly. In the UK, forensic investigators used DNA evidence to solve the ‘Black Pad’ murders and identify the killer as one Colin Pitchfork. It was later confirmed to be true when Colin confessed to his crimes. Ever since then, there have been countless investigations involving DNA evidence, court cases, legislation and more advanced research on DNA and genetics (Forensicscience.ie, 2014).
Structure of DNA:
DNA information is stored as code which consists of four chemical bases namely: adenine (A), guanine (G), cytosine (C), and thymine (T). The DNA in humans comprises at least 3 billion bases, 99 percent of which are similar in all persons. However, it is the ordering and sequences of these base pairs that determine the genetic information required to build and maintain an organism (Ghr.nlm.nih.gov, 2014).
DNA bases pair with each other such that A pairs with T, and C with G. These pairs are referred to as base pairs. Each base also has a sugar molecule and a phosphate molecule attached to it. The combination of a base, sugar molecule and phosphate molecule is referred to as a nucleotide. Nucleotides are arranged to form a double stranded, spiral shaped structure known as a double helix. The double helix structure resembles a spiral ladder such that the base pairs represent the rungs while the phosphate and sugar molecules form the vertical ladder sidepieces (Ghr.nlm.nih.gov, 2014).
DNA can replicate (make copies of itself) and thus each strand in the double helix structure may serve as a pattern for base sequence duplication. Replication is required during cell division since each new cell requires an exact copy of the DNA in the initial cell (Ghr.nlm.nih.gov, 2014). During the replication, the double strand DNA unwinds so that it can be copied but at other times, the unwinding is done so that the coded instructions can be used for protein synthesis and other biological processes. However, during cell division, DNA exists in its normal form (without unwinding) to enable its transfer onto the newly created cells. Organisms that reproduce sexually inherit half of each parent's nuclear DNA, but all mitochondrial DNA from the female parent. The phenomenon arises because egg cells as opposed to sperm cells are the ones that retain their mitochondria during fertilization (Genome.gov, 2014).
How DNA sequences are used in protein synthesis:
The use of DNA in protein synthesis involves two steps. The first step is the reading of information from the DNA molecule which is done by enzymes which then transcribe it onto an intermediary molecule referred to as the messenger ribonucleic acid, or mRNA (Genome.gov, 2014).
In the second step, the information in the mRNA molecule is used to create the essential building blocks of protein referred to as amino acids. In this case, the information is used to prescribe the precise order in which the amino acids must be linked to produce each specific protein. This task is quite important as more than 20 types of amino acids exist and can be ordered differently to produce a variety of proteins (Genome.gov, 2014).
Applications of DNA technology:
Since the unraveling of the DNA molecule structure by Watson and Crick, DNA technology has allowed scientists and researchers to examine, alter and create new genetic material. The applications are multidisciplinary, ranging from cellular functional mechanisms investigation, criminal identification in forensic science to the creation of new biological products.
DNA is used to reveal important biological processes and the diseases that result when these processes are altered thus helping them to understand the mechanisms of biological life. In forensic science, DNA is used to identify criminals and solve mysteries using biological material left behind by the perpetrators (Dnacenter.com, 2014).
DNA technology has also led to advancements in health and nutrition through the use of recombinant DNA technology that allows scientists to transfer genes among organisms thus producing new traits, organisms and products. For example, in 1997 scientists successfully cloned a sheep known as Dolly and since then, there have been similar advancements in medicine such as cancer treatments and tissue engineering. In agriculture drought and pest resistant crops have been created while advances in animal husbandry have led to the creation of growth hormones and transgenic animals (animals with recombinant DNA). DNA technological applications thus have tremendous discovery potential and applications as one of the new frontiers in biological sciences (Moulton, 2004).
Legal and Ethical considerations of DNA research:
As earlier mentioned, DNA technology has massive potential applications and thus there are various challenges that require to be addressed on the use of this technology. This is essential so as to ensure that research, innovation and treatment using DNA technology continues well without violating the confidence and trust of the general public. The legal-ethical issues need to address questions such as who has the right to cure what, why and how, the cost and availability of this technology to the public, who has the right to obtain and use genetic material, and finally whether anyone has the right to alter human genetics and control the outcomes of new generations. Issues regarding the safety of handling genetic material, possible use of DNA technology for malicious purposes such as creation of pathogens, and all other issues including unintended outcomes of genetic modification need to be addressed. In this case, the necessary legislation and ethical policies should be put in place to ensure control of this domain.
References:
Dnacenter.com,. (2014). DNA Technology is a Powerful Set of Techniques that Allow Scientists to Study and Manipulate Genetic Material. Retrieved 26 May 2014, from http://www.dnacenter.com/science-technology/dna-technology.html
Forensicscience.ie,. (2014). Forensic Science - The History of DNA. Retrieved 21 May 2014, from http://www.forensicscience.ie/Services/Forensic-Areas/DNA/The-History-of-DNA/
Genome.gov,. (2014). Deoxyribonucleic Acid (DNA) Fact Sheet. Retrieved 22 May 2014, from http://www.genome.gov/25520880
Ghr.nlm.nih.gov,. (2014). What is DNA? - Genetics Home Reference. Retrieved 27 May 2014, from http://ghr.nlm.nih.gov/handbook/basics/dna
Moulton, G. (2004). The complete idiot's guide to biology (1st ed.). Indianapolis, IN: Alpha.
Watson, J., & Crick, F. (1953). A structure for deoxyribose nucleic acid. Nature, 171. Retrieved from http://www.exploratorium.edu/origins/coldspring/printit.html
