[16] He joined the faculty in the Department of Microbiology at the Johns Hopkins University School of Medicine in 1972, where he began to exploit viruses as potentially powerful model systems for exploring the mechanisms of DNA replication in human cells.
[17] Using proteins derived from human cells, he and his colleagues developed the first cell-free DNA replication systems capable of duplicating the complete genomes of adenovirus and SV40.
Thus, biochemical analysis of the SV40 system made it possible to identify and functionally characterize proteins and enzymes that carry out the duplication of the chromosomal DNA in human cells.
[19] In subsequent work Kelly and colleagues have shifted their focus from studying the machinery of DNA replication to the mechanism that controls it.
[23] Kelly also led the establishment of the Gerstner Sloan-Kettering Graduate School of Biomedical Sciences, which provides a novel curriculum in basic and translational cancer biology leading to the Ph.D.