![]() ![]() Most polymorphisms are located in the estimated 95% of the human genome that does not encode for proteins ( 1). Such variable sequences are termed ‘polymorphic’ (meaning ‘many forms’) and are used for human identification, paternity testing, and diagnosis of genetic diseases. The information content of DNA resides in the sequence of bases, and although the DNA sequence in different individuals is more similar than different, many regions of human chromosomes exhibit a great deal of diversity. Each parent contributes a chromosome to the pair an individual inherits. Chemically, the DNA molecule is a highly stable polymer composed of subunits known as nucleotides, and in humans makes up the 22 pairs of autosomal and single pair of sex chromosomes. ![]() It encodes the genetic information in most organisms and is identical in every cell of an individual. The advent of DNA markers allowed for greater precision and higher discriminatory power in forensic testing.ĭNA is the vehicle for generational transfer of heritable traits. However, these suffered from low polymorphism, poor stability and restricted activity of the molecules, and the limited resolution of the detection methods. Earlier, identification procedures employed for the characterization of biological specimens were protein or ‘classical’ markers such as the ABO blood group antigens, serum proteins, and RBC enzymes. Variability in biomolecules has been exploited for identification of the source of the biospecimen. Deoxyribonucleic acid (DNA) technology has gained wide acceptance in crime investigations involving biological evidence, such as murder (blood evidence), sexual assault (semen evidence), murder with sexual assault (blood and semen evidence), or in cases of mass disasters (saliva evidence and body tissues), and in identification of mutilated bodies and exhumed skeletons (tissues and bones). Biological specimens recovered from the scene of crime provide remarkably valuable information about the crime and the personnel involved. Investigation of violent crime has always been a driving motivation for law enforcement agencies in any country, and more so in developing countries. Forensic science aids in the personal identification process by comparative methods or by enabling a profile of the individual regarding age at death, and sex, in crime investigations involving biological evidence, such as murder, sexual assault, and disaster victim identification. ![]()
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