In recent decades, scientists have gone to Frankenstein-like lengths to find solutions to some of the most pressing issues facing today’s society, particularly the spread of disease.  By modifying existing animal DNA, researchers have been able to engineer anything from glow-in-the-dark sheep to goats that spin spiders’ silk.And though it seems more like weird science fiction than fact, these altered animal species are very real and could potentially lead to greater developments in the way of medicine and environmental health, according to the Food and Drug Administration.   Here are some of the most notable examples of genetically engineered animals to come out of labs in the past 20 years.