Programmed DNA elimination

In most multicellular organisms, cells within an individual have essentially identical genomes. This principle underlies the ability to reprogram fibroblasts into induced pluripotent stem cells using defined transcription factors, clone a frog by transferring a nucleus from a tadpole somatic cell into an enucleated egg, and form totipotent callus cells by wounding plants. However, an exception to this one-body-one-genome principle exists in our blood cells. In developing lymphocytes in vertebrates, a process termed V(D)J recombination shuffles the antigen-binding regions of immunoglobulins and T-cell receptors.