Apoptosis or programmed cell death is a controlled and highly regulated process in mammalian cells. There are two main pathways: extrinsic an intrinsic. The extrinsic (death receptor) pathway relies on extracellular signals (ie Fas ligand, TRAIL) to activate proximal caspases (caspases 8 and 10) leading to cleavage and activation of the executioner caspases 3, 6 and 7. The intrinsic (mitochondrial) pathway requires disruption of the mitochondrial membrane causing release of the proteins Smac/Diablo, Omi/HtRrA2 and cytochrome C. Apoptosome formation subsequently occurs which results in caspase 9 activation followed by activation of the executioner caspases 3, 6 and 7. Sufficient overlap of these two major pathways occurs allowing extrinsic pathway agonists to influence intrinsic pathway activators and vice-versa. A number of upstream and downstream genes affect apoptosis and these genes are represented in this PCR array product.