Stem cells: science, policy, and ethics
J. Clin. Invest. Gerald D. Fischbach, et al. 114:1364 doi:10.1172/JCI23549 [Go to this article.]

Figure 4
Normal development versus development during reproductive cloning and therapeutic cloning. During normal development (A), after fertilization, a diploid zygote is formed, which then undergoes cleavage to form a blastocyst that may be implanted in the uterus and result in a live birth. During reproductive cloning (B), the diploid nucleus of an adult donor cell is introduced into the enucleated oocyte. Following artificial activation, division results in a cloned blastocyst. Upon transfer into a surrogate mother, a small number of cloned blastocysts give rise to a clone. Therapeutic cloning (C) requires the explantation of cloned blastocysts in culture to yield an ESC line able to differentiate in vitro into any type of cell for therapeutic purposes. Figure modified with permission from the New England Journal of Medicine (31).