the cells apart and may be the killing mechanism. Currently we focus on two major directions: Proteases other than caspases (proteases with very restricted substrate specificity that are the major proteases in apoptosis) and the acquisition by an embryo of the ability to undergo apoptosis. These studies have taken us, including many students, to many countries including (2000-2002) Canada, Spain, Italy, Sweden, Switzerland, Israel, Austria, and Australia. References External links PubMed list of scientific publications Google Scholar citations 1937 births Harvard University alumni 21st-century American biologists Living people American twins