Genetic Fingerprinting in Paternal Testing and Forensic Science - Research Paper Example

Introduction Genetic fingerprinting is a technique that relies on exploiting the differences between human DNA sequences, particularly in variable number tandem repeats (VNTRs), for identification. Predominantly the technique is used in paternity testing and the forensic sciences, and can be used as evidence in a criminal trial (Sheindlin 1996). The use of these VNTRs relies on the fact that these are highly variable between non-related humans and so any matches that are made, either between two individuals or forensic evidence and an accused, is not likely to arise by chance (Toth 1997).

The purpose of this essay is to explore the applications of genetic fingerprinting technology in paternal testing and forensic science, as well as highlighting some of the pitfalls of using such technology, particularly in a legal setting. Genetic Fingerprinting The principles of genetic fingerprinting rely on the differences between human genomic sequences. Although 99% of the human genome is the same in structure, there are certain differences (known as polymorphisms) that are distinctly different in individuals that are not related.

For example, VNTRs, particularly short tandem repeats (STRs or microsatellites) are molecular markers that are extremely prone to mutation (Gill et al 1987). All human genomes contain STRs, but these vary hugely between populations and within them, to the extent that 1 in 5 million people will have the same sequence by chance (Jeffreys, Wilson & Stein 1985). Any technique that can ascertain whether two DNA samples match will, therefore, reduce the possible number of perpetrators hugely, making genetic fingerprinting immensely useful to the law.

Related individuals also have similarity due to the STRs being co-dominant; each offspring will have one allele from each parent. It is this fact that makes genetic fingerprinting useful in paternity testing (Jeffreys et al 1985). Genetic profiling can occur in a number of ways. One of the most common is polymerase chain reaction (PCR) which amplifies the amounts of a specific DNA sequence, which is evidently useful when working with known STRs. This is achieved using oglionucleotide primers as well as a DNA polymerase, with the primers targeting a specific STR and the DNA polymerase amplifying them for analysis (Welsh & McClelland 1990).

It is important that multiple STRs are analysed using PCR, because each individual one can be shared by around 5-20% of the population (Sheindlin 1996). Using multiple STRs for analysis greatly increases the probability that an exact match will be made for whatever reason the analysis is occurring. This method relies on the principle of independent assortment, and the product rule for probabilities means that the chance of someone having the same alleles at multiple STR loci decreases with the number of loci analysed.

Genetic Fingerprinting in Paternal Testing It is because of the nature of VNTRs that makes them useful for paternal testing; because they are co-dominantly inherited, each individual will inherit one copy from each parent. This means that when trying to ascertain paternity, an individual will have the same sequence at each VNTR locus as the father (as well as one from the mother at the corresponding locus). If the mothers VNTR genotype is known, then these