Split Embryo Success

From cloning mice and sheep, the scientists of yesterday wondered if cloning humans was a possibility. In order to get as close to this goal, without breaking cloning laws, they turned to monkeys, one of our closest ancestors.

In early 1999, Tetra the Rhesus monkey was born via split embryo cloning. For the medical world, this was one step closer to human cloning. Unfortunately, this enthusiasm was not met by all, with the current ethical issues which arise from cloning such as animal rights and fear of loss of genetic diversity.


Tetra was created by split embryo. This complicated process involves creating a fertilised egg with sperm and egg from the father and mother respectively. Once the cell had reached the eight cell stage (blastula) the cells were separated and divided into groups of two and put into zonae (egg protective coating). Two of these embryos were then implanted into two different surrogate monkeys and left to grow naturally. Although one of the surrogate mother’s miscarried, the second implantation resulted in a female Rhesus monkey, Tetra.

Unlike somatic cell cloning, where the offspring will be clones of their parents, split embryo cloning results in offspring different to their parents (due to genes from both the father and mother), but all offspring from the one split egg are said to be twins, or genetically identical.

The disadvantage of this research is that the phenotype of the offspring is not know until after birth, and therefore cannot be selected for.

On the other hand, this type of research has led to similar processes happening in humans, where offspring are genetically selected for medical purposes.

Samantha Cavanagh 41290970

http://www.crystalinks.com/cloningmonkey.html
http://archives.cnn.com/2000/NATURE/01/13/monkey.cloning/
http://www.american.edu/TED/dolly.htm
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=14733750