Reproductive cloning is a technology used to generate an animal that has the same nuclear DNA as another currently or previously existing animal. In a process called "somatic cell nuclear transfer" (SCNT), scientists transfer the nucleus of a donor adult cell into an egg from which its genetic material has been removed. The reconstructed egg containing the DNA from a donor cell must be treated with chemicals or electric current in order to stimulate cell division. Once the cloned embryo reaches a suitable stage, it is transferred to the uterus of a female host where it continues to develop until birth.
In vitro transfection of cultured cells combined with nuclear transfer currently is the most effective procedure to produce transgenic livestock because SCNT allows the immediate use of cloned transgenic animals to be tested for the expression pattern of a given transgene. |