In recent years, scientists have mixed the DNA of a jellyfish with that of a monkey, creating a "transgenic" animal that glows in the dark. ("Transgenic" means possessing the genes of more than one type of organism.) Scientists have also inserted spider DNA into the genes of goats, creating ewes that produce milk containing spider-web silk. The goal of the project is to extract sufficient web silk — one of the strongest and lightest substances known — to create an industry in spider-silk products.
Other researchers are creating transgenic animals that contain minute quantities of human DNA. For example, the team that stunned the world with Dolly the cloned sheep, hope to genetically engineer cloned animals that produce human enzymes and proteins in their blood or milk, and then extract these substances — a process known as "pharming" — for use in the manufacture of human medicines.