1938: Hans Spemann, a German developmental Biologist, first suggests a nuclear transfer experiment to test the importance of the nucleus in early stage development. He was unable to complete the experiment.
Spemann H: Embryonic Development and Induction. New Haven, CT. Yale University Press. 1938
1950’s: Briggs and King report first nuclear transfer success in amphibians. Conclude that using an adult cell to clone is impossible.
1970’s: Developmental Biologist, John Gurdon, successfully cloned frogs using later stage cells. This experiment discounted the conclusion of Briggs and King and raised interest in the possibility of using adult cells in cloning experiments.
3/7/96: Announcement by Roslin Institute scientists of the successful production of two live sheep, named Megan and Morag, by transplanting nuclei from embryonic sheep cells.
K.H.S.Campell et al. "Sheep cloned by nuclear transfer from a cultured cell line." Nature 1996: vol. 380: pg 64-66.
2/23/97: Announcement of the existence of Dolly the lamb, first clone of an adult mammal.
I. Wilmut et al. "Viable offspring derived from fetal and adult mammalian cells." Nature 1997; vol. 385: pg. 810-813
3/5/97: President Clinton bans federal funding of human cloning by issuing a five year moratorium.
1/21/98: Advanced Cell Technologies in Texas successfully clone transgenic calves, calves that have been genetically manipulated. The goal is to be able to clone calves that have been genetically altered to produce human pharmaceuticals in their milk.
7/23/98: Announcement of second successful cloning of adult mammal in December, 1997, a mouse named Cumulina. By the time of the announcement, scientists in Hawaii had created dozens of cloned mice.
T. Wakayama et al. "Full-Term development of mice from enucleated oocytes injected with cumulus cell nuclei." Nature 1998; vol 394: page 369
8/20/98: Scientists in New Zealand report successful cloning of the surviving member of a rare breed of cow.
11/13/98: Biotech company in Massachusetts announces that it has successfully created a human clone using a cow egg. They report that they do not allow the embryos to grow past the 14-cell stage.
12/9/98: Several calves cloned from a single adult cow by Japanese scientists.
Y. Kato et al. "Eight Calves Cloned from Somatic Cells of a Single Adult." Science 1998; vol 282: page 2095
1/29/99: Oregon researchers report repeated unsuccessful attempts to clone monkeys, suggesting difficulties in human cloning.
D. Wolf et al. "Nuclear Transfer in the Rhesus Monkey: Practical and Basic Implications." Biology of Reproduction, page 199-204, 1999
5/27/99: Scientists report that Dolly’s cells inherited the age of the six year- old ewe from which she was cloned.
Nature 1999; vol 399: pages 316-317