The first draft of the human genome DNA sequence was reported in 2001 independently by the Human Genome Project and Celera Genomics [1, 2]. Since this important landmark in medical research, the entire research community has had access to a wealth of information that would otherwise have taken many years to gather, resulting in a tremendous acceleration of virtually all research studies that involve human biology or disease. With updates of the project, the sequence is nearly complete [3, 4]. It is interesting, however, that the number of genes in the human genome appears to be much smaller than initially estimated. Although the exact number of genes in the genome still remains unknown, more recent estimate for the number of protein-coding genes is between 20,000 and 25,000 [5], which markedly differs from the previously predicted number of approximately 100,000 [6-9]. The currently estimated gene number, of course, appears quite small, considering the complexity of our species. However, the difference between the older and most recent predictions of the gene number can be accounted for by the presence of multiple transcriptional
