An oocyte can reprogram an adult nucleus into an embryonic state after somatic cell nuclear transfer, so that a new organism can be developed from such cell. Reprogramming is distinct from development of a somatic epitype, as somatic epitypes can potentially be altered after an organism has left the developmental stage of life. During somatic cell nuclear transfer, the oocyte turns off tissue specific genes in the Somatic cell nucleus and turns back on embryonic specific genes.