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 units associated with many individual genes. In fact, the total number of proteins encoded by the human genome may be similar to, if not higher than, the past estimates of the gene number. This review focuses on the GNAS locus, which exemplifies a complex gene with multiple gene products derived through alternative promoter use and alternative pre-mRNA splicing.
