What is cloning?

By Dr Aleona Swegen

Cloning is the production of genetically identical individuals by non-sexual means.

Cloning by nuclear transfer involves the transfer of genetic material from one animal into the oocyte (egg) of another, and transfer of the embryo into a recipient mare to be carried to term.

Clones are genetically identical to their donors, but generally will not be exactly identical in appearance and behaviour. The greatest differences are associated with embryo transfer. These changes are present in all embryo transfers however are more obvious with cloned animals because we know what the expected outcome is. Environmental factors such as uterine blood supply, placentation, birth, milk, dam/foal nutrition will affect the foal. Later on, the handling and exercise, nutrition, vaccination, worming etc will mean that the animal is not the same as the original.

Although the clone itself may not be phenotypically identical to the donor, the genetic material IS exactly the same and therefore the offspring of the clone and donor are equivalent. Clones are able to reproduce normally.

A male clone’s foal cannot be distinguished from a donor’s foal, whereas a female clone’s foal can be distinguished by differences in the mitochondrial DNA. In the case of a stallion clone, no cytoplasm and therefore no mitochondria are transferred with sperm in fertilisation. Therefore a stallion clone will not pass on the mitochondrial DNA that he himself acquired from the ‘random’ oocyte in nuclear transfer, and subsequently a stallion clone’s foals are genetically indistinguishable from the donor’s foals.

For a more detailed description of cloning download the below pdf file. Tip: For explanatory notes hover your cursor over the brown speech bubble in the top left hand corner of each page.

Equine Cloning presentation (705 KB)

The Australian Performance Horse 2011 Yearbook featured an article Horse cloning - earning itself a controversial profile, also authored by Dr Aleona Swegen. Click on the link below to read the article.

Horse cloning, Australian Performance Horse Yearbook 2011 (1.7 MB)