INTRODUCTION
The process of DNA fingerprinting was invented by Alec Jeffreys at
the University of Leicester in 1985. He was knighted in 1994.
DNA fingerprinting or DNA profiling, any of several similar
techniques for analyzing and comparing DNA from separate sources,
used especially in law enforcement to identify suspects from hair, blood,
semen, or other biological materials found at the scene of a violent crime.
It depends on the fact that no two people, save identical twins, have
exactly the same DNA sequence, and that although only limited segments
of a person's DNA are scrutinized in the procedure, those segments will
be statistically unique.
PRINCIPLE OF DNA FINGERPRINTING
The human genome consists of innumerable small noncoding
sequences which are inheritable and repeatedly present. They can be
separated from the bulk DNA as satellite upon performing density
gradient centrifugation and thus known as satellite DNA. They can be
categorized into either microsatellites or microsatellites depending on the
length, base composition and tandemly repetitive units. These satellite
DNA show polymorphism and this polymorphism is the basis of DNA
fingerprinting. The repeat regions can be divided into two groups based
on the Size of the repeat variable number tandem repeats (VNTRs) and
short tandem repeats. These repeats act as genetic markers and every
individual inherits these repeats from their parents. Thus. every individual
has a particular composition of VNTRs and this is the main principle of
the DNA fingerprinting technique.
History of DNA Fingerprinting
Up to 1984, the only method of establishing and authenticating
personal identification was by the fingerprint process.
DNA fingerprinting technique was devised in 1985 by Alec
Jeffrey at University of Leicester in England, while working on
the sequences within myoglobin gene.
What is DNA Fingerprinting?
It is a technique, by which an individual can
be identified at molecular level. With the
advancement of science and technology STR
analysis has become very popular in forensic
laboratories. Scientists have chosen repeating
sequences in the DNA, which are present in all
individuals on different chromosomes, and are
known to vary from individual to individual
except in identical twins. These are used as
genetic markers to identify the Individual.
DNA fingerprinting technology
DNA fingerprinting technology has
made it possible to identify the source of
biological samples found at scenes of
crime. This will resolve disputes of
maternity/paternity, identification of
mutilated remains, identification of rape/
murder, identification of missing child, exchange of babies in hospital
wards, forensic wildlife, protection of farmers rights and biodiversity.
This remarkable technology provides exclusion as well as positive
identification with virtually 100% precision.
Biological Material Used for DNA fingerprinting
Blood Hair Saliva
Semen
Body tissue cells
DNA samples have been obtained from vaginal cells transferred to
the outside of a condom during sexual intercourse.
Stage of DNA Fingerprinting
Cells broken down to release DNA
DNA strands cut into fragments
Fragments separated
Pattern of fragments analyzed
DNA fingerprinting: Methods
A common procedure for DNA fingerprinting is restriction
fragment length polymorphism (RFLP). In this method, DNA is
extracted from a sample and cut into segments using special
restriction enzymes. RFLP focuses on contain sequences of
repeated DNA bases, which vary widely from person to person.
The segments are separated using a laboratory technique called
electrophoresis, which sorts the fragments by length. The segments
are radioactively tagged to produce a visual pattern known as an
autoradiograph, or DNA fingerprint, on X-ray film. A newer
method known as short tandem repeats (STR) analyzes DNA
segments for the number of repeats at 13 specific DNA sites. The
chance of misidentification in this procedure is one in several
billion. Yet another process, polymerase chain reaction , is used to
produce multiple copies of segments from a very limited amount of
DNA (as little as 50 molecules), enabling a DNA fingerprint to be
made from a single hair. Once a sufficient sample has been
produced, the pattern of the alleles (see genetics ) from a limited
number of genes is compared with the pattern from the reference
sample. A nonmatch is conclusive, but the technique provides less
certainty when a match occurs.
DNA fingerprinting: Applications
DNA fingerprinting can be applied in the following scenarios:
Establishment of paternity and Maternity
Establishment of the parentage for child swapping cases
Establish the identity of the rapist in rape cases
Identification of mutilated remains In murder, bomb blast, air
crashes etc.
Wild life identification.
CONCLUSION
In conclusion, while evidences can be tampered with and witnesses
can turn hostile, DNA will never lie. It will indeed, unravel the truth even
several decades after a crime has been committed. Such are the powers of
DNA Fingerprinting.
BIBLIOGRAPHY
1. Google.com
2. Class 12th Biology Book
3. Wikipedia.com
INDEX
1. Introduction
2. History of DNA fingerprinting
3. What is DNA fingerprinting
4. DNA fingerprinting technology
5. Biological material used
6. Stages of DNA fingerprinting
7. Methods of DNA fingerprinting
8. Application of DNA fingerprinting
9. Conclusion
10. Bibliography
