The human genome project: its implications in clinical medicine.

The greatest impact of the Human Genome Project on clinical medicine is the appreciation of the extra-ordinary molecular and biochemical individuality of each patient. Gene polymorphism occurs in 1 in 1000 DNA base pairs in the human genome. This is reflected in the diversity of the gene products structural proteins, enzymes, channel proteins, transporters and binding proteins, receptors and post-receptor signaling cascades. Polymorphism can occur not only in the protein-coding sequences but also in the upstream promoter sequences such polymorphism can influence the activities of several enzyme-mediated processes. The most common gene polymorphism is single nucleotide polymorphism ( SNP ). There are over 3 million SNPs in the entire human genome, out of which 60,000 are in the exons or coding regions of DNA ( cSNPs ) which help in the hunt for genes of clinical interest. There are, on an average 4-8 SNPs in every gene either in the exons or in the nearby exon-intron boundaries in the upstream regulatory regions SNPs in coding regions ( 1 per 346 bp ); SNPs in non-coding regions ( 1 per 354 bp). Each person would be heterozygous for 24,000 40,000 non-synonymous (aminoacid altering ) substitutions. Gene of interest can be pin-pointed using SNPs. At the molecular level mutations in gene, leading to altered gene products or altered regulation of gene expression provide an