Embryo cloning is a relatively new technique. It is used with embryos from the best stock animals available, or from genetically engineered embryos which are capable of producing human medicines in their milk. It is a big step on from embryo transfer.

In embryo transfer the best breeding animals are stimulated by hormones to released many fertile eggs at the same time. The eggs are fertilised and the early embryos are then flushed out of the uterus of the biological mother and transplanted into a number of surrogate mothers. Using this technique, some cows have produced fifty calves a year!

In embryo cloning, early embryos are collected in the same way. At this very early stage of embryonic development every cell is still totipotent – capable of forming all of the cells needed for a new organism. So each embryo is divided into individual cells, given special nutrients and cultured in the laboratory for 6 to 7 days – by which time each cell will again be a developing embryo. At this stage they may be implanted into surrogate mothers or they may be divided yet again to produce even more identical embryos.

This ‘artificial twinning’ is mainly used to make lots of identical copies of embryos which have been genetically modified to produce medically useful compounds. Amazingly, the cloned embryos can even be implanted into the uterus of a rabbit, or frozen, and carried across the world before they are finally implanted into the surrogate mother which will carry them until they are born. Click on the image to open a larger version of it in a new page

Because this technology largely involves farm animals and has only benefits for humans beings there has been relatively little ethical debate about the development of embryo cloning.