DNA is located in the cell nucleus and called as nuclear DNA. A small amount of DNA can be found in the mitochondria, where it is called as mitochondrial DNA. DNA has the ability to replicate and make copies of itself. The double-helix structure of DNA was presented by James Watson and Francis Crick in April 1953. They won a Nobel Prize in Physiology or Medicine for their discovery in 1962.
DNA stores all the information with the help of four chemical bases; adenine(A), guanine(G), which are called purines and cytosine(C) and thymine(T), called as pyrimidines. These base pairs are attached to a sugar and a phosphate molecule. Thus, a base pair, sugar molecule and phosphate molecule form a nucleotide. The two long strands of nucleotides forming a spiral is called a double helix. This double helix looks similar to a ladder. The sequence in which these base pairs occur determine the formation of various traits and building of an organism.
DNA is also found in the plants. All living organisms use the same principle of storing information - DNA and RNA. DNA is unique to each individual like fingerprints. Thus, DNA can be mapped to reveal the genetic make up of an organism. The technique of DNA fingerprinting was discovered by geneticist Alec J. Jefferys in 1984. He was carrying out studies on the gene for myoglobin. DNA fingerprinting in plants is used for protection of the ecosystem, identifying marker traits, identification of gene diversity and variation and mutations. There are various methods for plant DNA fingerprinting like Restriction fragment length polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Amplified fragment length polymorphism (AFLP) and Simple Sequence Repeats (SSRs).
DNA fingerprinting in plants involves the extraction of DNA from plant cells, quantification and quality assessment. While carrying out polymerase chain reaction (PCR) based duplication of DNA in RAPD, ISSR or SSR, diluted DNA is mixed with a master mix. The master mix contains PCR buffer, DNTPS, primer, water and Taq polymerase enzyme in a PCR eppendorf tube. The PCR machine is pre-programmed for the number of cycles, the DNA mixture is loaded and the cycle is carried out. After the cycle is completed, electrophoresis of the samples is carried out. AGE or PAGE electrophoresis can be used depending upon the technique. The samples are stained to reveal the banding patterns. After DNA has been isolated and enough copies of DNA are replicated, various methods explained below are used for DNA fingerprinting.
