What is DNA testing?
Deoxyribonucleic Acid is the genetic material in most of the living beings on planet world. Each individual has a unique set of DNA which is also a characteristic or profile of that individual. In forensic science the need for identifying a person through his genetic basis aroused when no other clue was left which could give proper details related to that person. Based on this requirement of the forensic sciences a technique called DNA testing was developed in which a person is identified by the patterns of his or her DNA. As no two individuals can ever have the same DNA this technique proved great help in solving many crucial cases and also led to many important discoveries.
The other names that have been given to this technique of DNA testing are DNA profiling, DNA typing and also Genetic fingerprinting. All of these terms indicate the same technique and methodologies. Since this technique is based on the DNA profiles it is important to know what DNA profiles are to understand the mechanism of this technique. The entire DNA Built of an individual is in the set of an encrypted language this is termed as DNA profiles. These DNA profiles are the genetic identity of a person and this is the code which differentiates us from the rest of the world.
In the human body only a 0.1% of the DNA is different from the other person. Almost 99.9% of the DNA is alike in all the humans. But this mere difference of 0.1% makes every individual dissimilar. For this technique of DNA testing VNTR’s are used. VNTR are Variable number tandem repeats. These are the DNA profiles which are variable and repetitive in the entire DNA of the person. The loci of VNTR can never be similar in two unrelated people. All this basic information is used for DNA testing of a person.
How it is done?
The course of action for DNA testing of a person is initiated by simply taking the sample of DNA of a person. Buccal swab is used for collecting DNA sample so that the reference sample does not gets contaminated any how. The DNA of another person (Supposed to be his relative) is also taken so that later comparisons can be made whether the person examined is linked to that person or not. After collecting the reference samples techniques like PCR, RFLP analysis, STR analysis are used for making a DNA profile of that person.
RFLP analysis: This was the most primitive method for profiling a person’s DNA which made use of restriction enzymes and then later the technique of southern blotting. This technique was overall very arduous and this is why it was later reinstated with PCR assays.
PCR analysis: The discovery of this method for DNA testing greatly reduced the complexity of the entire procedure and also improved the final outcome. PCR is polymerase chain reaction and in this technique the DNA of the person is amplified greatly which results in the examination of a small part of the DNA perfectly. This method is also sympathetic for identifying the loci of VNTR.
STR analysis: in this method short tandem repeats are used for profiling a person’s DNA using the polymerase chain reactions. Since every individual has different STR’s therefore the identification of STR loci becomes easy through this method.
History of DNA testing
Two breakthroughs in the medical technology ultimately led to the discovery of this highly important and useful technique of DNA testing. Sir Allec Jeffery in the year 1984 discovered the technique of DNA fingerprinting in England and simultaneously in United States of America Kary Mullis developed the technique of polymerase chain reaction. Both of these discoveries were made individually but when the two techniques were used together it resulted out in the invention of the ultimate modus operandi of DNA testing.
In 1986 Sir Jeffreys used DNA for investigating a criminal. Samples which were stained in semen were used for DNA fingerprinting. The final result of this investigation was worth the time invested in this procedure. This is how this entire technique popularized and ultimately gave rise to better techniques like DNA testing.
Types and purpose of DNA testing
Two major types of DNA testing are available up till now. These are:
- Mitochondrial DNA Testing
- Y Chromosome Testing
Through the technique of mitochondrial DNA testing the maternity history of a person can be found out. In this the three regions coding region, HVR2 and HVR1 are tested. A hyper variable region signifies for the areas where more VNTR are available.
Y Chromosome DNA testing is used to the paternal history of a person. Y chromosome decodes the information that is only passed to a son from his father in the form of his Y chromosome.
The purpose of DNA testing is found majorly in identifying the suspects of a crime. DNA testing is mostly used in the forensic science for solving a case. The links between two people are identified through their DNA genetic basis. This technique has helped in solving many cases. In cases of murder, rape and accidents DNA testing technique is of great use because it helps in solving the case with great ease. A culprit can never runaway from his own DNA information. The DNA helps in getting that criminal caught which ultimately leads to a solution.
This is why DNA testing is regarded to be a major discovery in the world of forensic science. It is simplified the way cases were solved. This technique has also helped scientists in making the DNA genome of a person and also in coding and decoding the various bases and base pairs in a DNA. New techniques are added from time to time for updating this method of DNA testing and for making it more reliable and accurate. DNA testing is therefore a great tool for the world of forensic science as no culprit can run away from them now.