Ovine pulmonary adenocarcinoma as an animal model for human lung cancer, because OPA is histologically similar to human adenocarcinoma in situ of the lung. Dolly the sheep, the first mammal successfully cloned from an adult somatic cell, was euthanized after it was confirmed that she had OPA. Ovine pulmonary adenocarcinoma Ovine pulmonary adenocarcinoma (OPA), also known as ovine pulmonary adenomatosis, or jaagsiekte, is a chronic and contagious disease of the lungs of sheep and goats. OPA is caused by a retrovirus called jaagsiekte sheep retrovirus (JSRV). The disease has a long incubation period, and therefore signs usually occur in adult animals (over 2
Animal track some types of rock formations. These types of fossils are called trace fossils since they are a trace of an animal left behind rather than the animal itself. In paleontology, tracks often preserve as sandstone infill, forming a natural mold of the track. Animal track An animal track is an imprint left behind in soil, snow, or mud, or on some other ground surface, by an animal walking across it. Animal tracks are used by hunters in tracking their prey and by naturalists to identify animals living in a given area. Books are commonly used to identify animal tracks, which