Carnegie cell biologist Joseph G. Gall in the Department of Embryology was chosen to receive the 2007 Louisa Gross Horwitz Prize, awarded annually by Columbia University to recognize outstanding contributions to basic research in the fields of biology and biochemistry. Gall shares the 2007 award with Elizabeth H. Blackburn of the University of California, San Francisco and Carol W. Greider, of the Johns Hopkins University School of Medicine. Gall and his colleagues represent three generations of teacher-student scientists. The award honors their work on telomeres, structures that protect the ends of chromosomes during DNA replication. Telomeres diminish in size with each replication, ultimately limiting the lifespan of cell lines that lack the restoring enzyme telomerase. Research on telomeres and telomerase is fundamental to understanding the aging process and has implications for the growth of cancer cells.