Recombinant rat cells. Immunofluorescent light micrograph of genetically engineered (recombinant) rat cells. Oval nuclei contain blue stained DNA- genetic material and green stained nuclear matrix proteins. These proteins bind to DNA and hold it in chromosomal structures. These rat cells contain a human gene which is producing a recombinant protein, bcl, associated with cell death (or apoptosis). The bcl protein is stained red in the cytoplasm of the cells. The study of such proteins may lead to a greater understanding of the mechanisms of cell death and the causes of cancer. It may help lead to a genetic cure for cancer. Magnification: x624 at 6x4.5cm size.