The SNP mapping

Single Nucleotide Polymorphism or the SNP, as commonly referred to by genetic and biomedical researchers, is a common form of DNA or genetic variation -90% of all variations-that occur within an individual’s DNA sequence. [Brookes, 1999, pp: 177] The genetic code is specified by the four-nucleotide "letters" A (adenine), C (cytosine), T (thymine) and G (guanine). SNP variation occurs when a single nucleotide, such as an A, replaces one of the other three-nucleotide letters-C, G, or T. The change or alteration of the DNA segment AAGGTTA to ATGGTTA – the second "A" in the first sequence is replaced with a "T" in the second sequence – is an example of SNP. [NCBI, 2003]
SNPs occur about once in every 1,000 bases along the human genome. [Brookes, 1999, pp: 178] The high rate of occurrence of SNPs and their relatively regular distribution, present them as potential genetic markers in studying human genetic variation [Zhao et al, 1998 in Roses, 2000] Though many SNPs have no major effect on cell function, scientists suggest that certain SNPs are indicative of the susceptibility of an individual to diseases as well as the sensitivity or responsiveness to drug. [HGIP, 2004]
Otherwise a challenging task, the recent technological advances have enabled scientists to develop techniques to identify and map SNPs by comparing selected regions of a DNA sequence. The SNP map clearly delineates the position at which SNP are located on the human genome sequence. The potential applications of SNP in biomedicine and pharmacology have instigated researchers and scientists to create a high-density SNP map of the human genome that would be available for use by all researchers. It was with this aim that the SNP Consortium (TSC), constituting of world’s ten largest pharmaceutical companies, two information-processing companies, the Wellcome Trust and world-leading academic institutions, was launched in April 1999. the project aimed at identifying about 300,000 SNPs, and about half these to be mapped for future use. [Roses, 2000] The project eventually discovered about 1.8 million SNPs. [HGIP, 2004] The U.S. Human Genome Project (HGP) is another team involved in mapping SNPs in human genome. [HGIP, 2004]
The Significant Uses of SNP Maps
Research suggests that SNP maps present significant potentialities in biomedicine in areas including disease detection. medical diagnostics and individualized prescription of medicines. preventive and curative medicine. development of pharmaceutical products. and in drug surveillance. Variations in DNA sequence such as a SNP occurs in about 1% of the population, [Brookes, 1999, pp: 178] however these genetic variations greatly influence the individual’s response to diseases, bacterial and viral infections. response to chemicals and toxins. and also to drugs and other therapies. Apart from its extensive application in biomedical research, because of their genetic stability, SNPs also function as useful genetic or biological markers in population studies. [HGIP, 2004]
The SNP maps positively help physicians to identify the multiple genes associated with many complex diseases including cancer, diabetes, vascular disease, and also certain mental illnesses. [HGIP, 2004] These "susceptibility" genes though not