A Mule Cloned from Fetal Cells by Nuclear Transfer
Nuclear transfer was used to produce a cloned mule, a sterile hybrid equine species. Mules result from breeding a male donkey (Equus asinus, 62 chromosomes) with a female horse (Equus caballus, 64 chromosomes), producing an animal with 63 chromosomes. Equine cloning has been hampered by a lack of optimal in vitro oocyte maturation and embryo culture systems (1), and previous reports of nuclear transfer pregnancies have been less than 65 days of development in utero (2).
Woods, G.L., K.L. White, D.K. Vanderwall, G. Li, K.I. Aston, T.D. Bunch, L.N. Meerdo and B. Pate 2003. A Mule Cloned from Fetal Cells by Nuclear Transfer Science 301(5636): 1063.