Deoxyribonucleic acid, or DNA, is a biological molecule that contains the genetic instructions needed to control how all living things—including viruses—develop, grow, reproduce, and operate.
Nucleic Acids and Polynucleotides
The nucleic acids DNA and ribonucleic acid (RNA) are joined to proteins, lipids, and complex carbohydrates (polysaccharides). They belong to one of the four major types of fundamental macromolecules required for the development of all living beings (Altintas et al., 2012. 138). The majority of deoxyribonucleic acid fragments are constructed from double biopolymer pieces that are coiled into a two-helix shape. The double helical DNA fragments are referred to as polynucleotides because they result from simple monomer units known as nucleotides. A nucleotide is made of one from four nucleobases namely; guanine (G), cytosine (C), thymine (T) and adenine (A). These nucleobases contains nitrogen, a phosphate group and a sugar known as deoxyribose. Different nucleotides are linked together in a series by covalent links between the phosphate group one nucleotide with the sugar of the other one, yielding an interchanging sugar-phosphate strand. Bases of the two distinct polynucleotide fragments are attached, following the base coupling rules, where adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G), with hydrogen links to produce a double helix DNA (Altintas et al., 2012. 138).Genetic Variability and Profiling
Except for hereditarily identical twins, every person's genetic information is a unique arrangement of DNA series that play key roles in describing who each person is. Intense study is being done to know genetic variances among different people (Altintas et al., 2012. 138). By knowing how each person's genome varies from another's, it will be easy to uncover differences that are responsible for not only creating our separate behaviors, such as the way we walk but also for creating vulnerabilities to some diseases.DNA profiling which is also known as DNA fingerprinting, DNA typing or DNA testing is the method of studying a person's DNA physiognomies, known as DNA profile, which is much possible to be dissimilar in unrelated persons, thus being as distinctive to persons as the fingerprints (Morinha et al., 2012. 703). It is important not to confuse DNA profiling with total genome sequencing. Profiling of DNA is commonly employed as a scientific procedure in criminal inquiries to find an unidentified individual or whose information require to be established, or to locate an individual at any crime area or to exclude any person from being considered. Deoxyribonucleic acid profiling has as well been applied to help elucidate fatherhood, in immigration disagreements, in paternity testing as well as in genealogical study or medical study. DNA fingerprinting is also being used in studying of floral and animal populations as well as in fields of botany, zoology, and agriculture.Polymerase Chain Reaction (PCR)
PCR (Polymerase chain reaction) is a known laboratory procedure used to duplicate a particular segment of a DNA strand. This DNA segment can be containing any characteristic the researcher is looking at (Morinha et al., 2012. 703). For instance, it can be a genetic factor whose trait an experimenter desires to know, or a gene marker utilized by forensic researchers to connect crime area DNA with the suspect.Usually, Polymerase chain reaction aims to produce sufficient target DNA segment, so that it can easily be studied or utilized in any other way intended (Morinha et al., 2012. 703). For example, DNA multiplied by PCR technique can be used for sequencing, visualize through gel electrophoresis, or replicated into a plasmid for more experiments. PCR is applied in various areas of medicine and biology, including medical diagnostics, molecular biology studies, and some areas in ecology.Gel Electrophoresis
Gel electrophoresis is a method of separating DNA strands and other macromolecules like proteins and RNA using their charge and size. Electrophoresis includes running a current thru a gel that contains the molecule of interest (Morinha et al., 2012. 704). Due to their charge and size, the molecules move in different directions and at different speeds through the gel, letting them separate from each another. Gel electrophoresis can also be used to estimate the size of DNA molecules as well as analyze the PCR products.Theory
Agarose gel electrophoresis is the most popular as well as the easiest method of separating as well as examining DNA. The DNA fragments are divided by their charges by running an electric current to the electrophoretic device. Shorter fragments move more smoothly and relocate faster than larger fragments thru the pores in the gel, a process known as sieving (Morinha et al., 2012. 705). Agarose gel can be utilized to examine the DNA in to enumerate it or to detach a certain section. The DNA molecule can be observed in the gel when ethidium bromide is added.Movement of DNA fragments through the gel
First, the gel is applied to the box. All the DNA samples that are to be examined are carefully put into one well at the end of the gel. Another well is earmarked for a DNA molecule ladder, a control reference with DNA molecules of known sizes (Morinha et al., 2012. 705). The power is then switched on, and the current start flowing through the gel in the box. DNA molecules contain negative charges due to the phosphate group found in the sugar-phosphate outline; therefore, they start transferring through the medium of the agarose gel heading to the positive end. The gel is referred to as running after the power is switched on, and the current is flowing through it.Shorter DNA fragments will move through the pores in the gel medium faster than long ones. After some minutes, the shortest DNA molecules will have moved near the positive pole of the gel box, but the longest DNA molecules will be found near the wells (Morinha et al., 2012. 705). The extent to which the molecules will move will be determined by:1. The weight of the RNA or DNA molecule - The size of the DNA fragment is a fundamental issue; shorter fragments travel farther.2. Voltage - The lower the amount of voltage, the slower the DNA molecules move. However, voltage is restricted by the fact that high voltage heats the gel hence causing it to melt. Also, the high voltage decreases the resolution.
Buffers
Several buffers have been endorsed for the electrophoresis process of DNA molecules. The regularly utilized buffers are TAE (Tris-acetate-EDTA) and TBE (Tris-borate-EDTA). The rate of movement of DNA molecules in these buffers is slightly different because of the variation in ionic strength. Buffers offer the ions that support conductivity (Morinha et al., 2012. 705).The agarose gel electrophoresis has advantages in that it is easy to pour the gel, it does not deform the samples, and it is easy to recover the samples. However, it has some disadvantages which are that the buffer can be exhausted, melting of gels during electrophoresis, and also different types of genetic molecules might run in changeable forms. When the experiment is over, the resulting agarose gel can be put in a plastic bag and be stored in a refrigerator.Work Cited
Altintas, Zeynep, et al. “Development of surface chemistry for surface plasmon resonance based sensors for the detection of proteins and DNA molecules.” Analytica chimica acta 712 (2012): 138-144.
Morinha, Francisco, João Alexandre Cabral, and Estela Bastos. “Molecular sexing of birds: A comparative review of polymerase chain reaction (PCR)-based methods.” Theriogenology 78.4 (2012): 703-714.
