Programmed chromosome breakage occurs at 50-200 specific sites in the genome of Tetrahymena thermo-phila during somatic nuclear (macronuclear) differentiation. Previous studies have identified a 15 bp sequence, the Cbs (for chromosome breakage sequence), that is necessary and sufficient to specify these sites. In this study we determined the effects of mutations in the Cbs on its ability to spe...

This study focused on several wetlands in Laguna del Tigre National Park (Guatemala) as part of Conservation International's Rapid Assessment Program. Sediment and water samples were collected from a laguna near Xan field, Guatemala's largest oil facility, and three other sites for determination of levels of polycyclic aromatic hydrocarbons (PAHs). Cichlid fish (Thorichthys meeki and Vieja syns...

FROM time to time one of my colleagues working at a medical school commiserates with me because I spend 40 hr a year lecturing to undergraduates. I always reply that teaching has compelled me to learn a lot of material that I would not have known about had I taught only my specialized subject. These forays into the ‘‘beyond’’ were instrumental in moving my research in new directions. Three arti...