Cloning animals
Cloning of animals became a reality when scientists at the Roslin Institute in Scotland created the famous sheep Dolly in 1997. She aroused worldwide interest and concerns about cloning because of scientific and ethical implications.
Roslin Institute, Edinburgh
Dolly was produced by a method called somatic cell nuclear transfer (SCNT). The nucleus from a mammary (udder) cell of an adult sheep was injected into a sheep egg cell. The original nucleus of the egg cell had been removed before the new DNA was injected. The egg was then inserted into the uterus of a different sheep, as though she had been fertilised by artificial insemination.
When Dolly was born she was an exact genetic copy (clone) of the animal from which the nucleus was taken - her genetic mother. That is, Dolly was genetically identical to the sheep from which the mammary cell nucleus was taken.
There is an important difference between Dolly and her 'mother', and a pair of identical twins. Identical twins are genetically identical because they developed from the same fertilised egg. Dolly and her 'mother' are genetically identical because Dolly's DNA came from a mature cell of her 'mother'.
Dolly was put down at the age of six, when it was discovered that she had a chronic lung disease. Her breed of sheep normally lives for between ten and twelve years. An extensive post-mortem was carried out on Dolly and no evidence was found to suggest that being a clone contributed to her early death.
Since Dolly, many other mammalian species have been cloned, including cows, pigs, mice and rats. Monkeys have also been cloned using a similar process to embryo splitting. Tetra, a rhesus monkey, was the first primate to be cloned using a method that splits the original cells in an embryo to make multiple identical animals. However, the cloning process is still inefficient: only around 3% of cell nuclei that are transferred to donor eggs result in live births.
The Roslin Institute in Edinburgh produced Dolly the sheep: http://www.roslin.ac.uk/
Try cloning your favourite dog using the same method to create Dolly – interactive
Try cloning an animal that is extinct – the thylacine – interactive
Australia’s first clones
Cooperative Research Centre for Innovative Diary Products
Australia's first cloned cow, Suzi, was born in April 2000.
In 2002 she gave birth to a healthy heifer calf called Suzitru, who was conceived by artificial insemination using semen from an elite bull called Truman. As expected of a top Holstein cow, Suzi milked well and the milk was analysed before being discarded. Tests showed the milk to be the same as milk from any other cow.
Suzi's twin sister Mayzi, likewise gave birth in 2001 to a healthy Truman daughter (called Mayhem). Unfortunately, shortly after giving birth, Mayzi contracted acute toxic mastitis (a condition that affects around 1% of dairy cows) and died soon after despite intensive veterinary treatment. In July 2004, Suzi also died after calving, due to acute mastitis.
Cooperative Research Centre for Innovative Dairy Products
Australia's first cloned bull, Rameses II, a clone of one of Australia's top dairy bulls at the time, is now an adult and is producing good quality semen. The semen from Rameses II is collected to demonstrate that he can produce semen normally, but it will not be used to inseminate cows.
Matilda was Australia’s first cloned sheep. She was born in April 2001 having been cloned by Dr Simon Walker and his team at the South Australian Research and Development Institute (SARDI). Matilda was produced using techniques similar to those that produced Dolly.
In February 2003, Matilda died of natural causes. Between Matilda’s birth in 2001 and early 2005, four more cloned sheep have been born and continue to show excellent health. The South Australian team are now looking at how cloned animals perform under various conditions; what causes problems that result in some cloned embryos not growing; and how cloning can be used to breed GM animals.
Calf clone with a difference
Researchers in Victoria combined genetic modification with nuclear transfer technology to produce a dairy cow with a new and valuable characteristic – an extra gene to produce higher levels of protein in her milk.
Skin cells were collected from an elite Holstein cow. They were placed in culture and genetically modified with an additional cow gene responsible for milk protein production. These cells were further cultured to reproduce millions of these GM cells, which were then used to create embryos.
Cooperative Research Centre for Innovative Diary Products
The embryos were then transferred into surrogate cows. In early 2002, Australia's first GM calves were born as a result of this research project undertaken though Monash University and Genetics Australia Cooperative Limited and supported by the Cooperative Research Centre (CRC) for Innovative Dairy Products. The four calves - Holly, Molly, Lolly and Jolly - had an extra gene for milk protein production – a first for the Australian dairy industry.
The technology is still in early stages and three of the clones died or were put to sleep to as they had health problems. Holly is the only calf to have survived. She continues to be a normal, healthy dairy cow and it is expected that this genetic modification will result in a higher protein content in Holly's milk.
Milk is recognised as a major source of nutrition, particularly calcium and protein. This research project was designed to investigate a means to efficiently increase milk's nutritional value. Once this technique is perfected, there is the potential to clone cows that produce milk containing vaccines and medicines.
For more information on dairy biotechnology research in Australia, go to the Cooperative Research Centre for Innovative Dairy Products: www.dairycrc.com.au