Abstract: A nuclear transfer embryo is formed by destabilizing microtubules of an oocyte, whereby essentially all endogenous chromatin collects at a second polar body during meiosis of an oocyte. The oocyte is fused with the nucleus of a donor somatic cell of the same species of said oocyte prior to cessation of extrusion of the second polar body from the oocyte, thereby forming the nuclear transfer embryo. In one embodiment, the nuclear transfer embryo is employed to impregnate an animal, such as a mammal. In another embodiment, the donor nucleus is transgenic.