Human Genome Project has revealed that up to-20% of the 32, 000 human coding genes encode proteins involved in signal transduction, including transmembrane receptors, G-protein subunits and signal- generating enzymesHuman Genome Project has revealed that up to ~ 20% of the ~32,000 human coding genes encode proteins involved in signal transduction, including transmembrane receptors, G-protein subunits and signal￾generating enzymes