Cloning animals
Cloning of mammals 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 the scientific and ethical implications of cloning.
Roslin Institute, Edinburgh
Dolly was produced by somatic cell nuclear transfer (SCNT). The nucleus of an egg cell from an adult sheep was removed and replaced with the nucleus from a mammary (udder) cell of an other adult sheep. The egg was then inserted into the uterus of a different sheep, where it developed into a sheep embryo just like a normal fertillised egg.
Dolly was an exact genetic copy (a clone) of the animal from which the mammary cell nucleus was taken — her genetic mother. But, although Dolly was genetically identical to her ‘mother', she was not her identical twin. Identical twins are genetically identical because they developed from the same fertilised egg, whereas Dolly's DNA came from a mature cell of her ‘mother'.
Dolly was put down at the age of six after developing a chronic lung disease. Her breed of sheep normally lives for ten to twelve years. An extensive post-mortem found no evidence to suggest that being a clone contributed to her early death.
Click on the image below to see how Dolly was cloned.
Since Dolly, many other mammalian species have been cloned, including cows, pigs, mice, cats, dogs and rats.
Monkeys have also been cloned; 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, Suzi gave birth to a healthy heifer calf called Suzitru, who was conceived by artificial insemination using semen from an elite bull called Truman. Tests of Suzi's milk showed it was the same as milk from any other cow.
Suzi's twin sister, Mayzi, 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 2004, Suzi also died after calving, due to acute mastitis.
Cooperative Research Centre for Innovative Dairy Products
Australia 's first cloned bull was born in 2002. Rameses II was a clone of one of Australia's top dairy bulls at the time. His semen was collected and analysed, and demonstrated normal fertility. Two other bull calves, Duncan and Slim, were also born in 2002, using a new, simplified cloning technique.
Matilda, Australia 's first cloned sheep, was born in 2001. She was cloned at the South Australian Research and Development Institute (SARDI). Matilda was produced using techniques similar to those that produced Dolly. She died of natural causes in 2003. Between Matilda's birth in 2001 and early 2005, four more cloned sheep were born and showed excellent health. SARDI researchers aim to develop the technology for use in livestock industries as well as to improve wool fibre production.
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: high-protein milk.
Milk is recognised as a major source of nutrition, particularly of calcium and protein. The researchers, from Monash University and Genetics Australia Cooperative Limited, supported by the Cooperative Research Centre (CRC) for Innovative Dairy Products, wanted to investigate methods to efficiently increase milk's nutritional value.
The scientists added a cow milk protein gene to skin cells collected from an elite Holstein cow. The genetically modified cells were cultured and used to create embryos that were transferred into surrogate cows.
Cooperative Research Centre for Innovative Diary Products
In 2002, fourteen GM calves were born that had the extra milk protein gene. They were Australia's first cloned calves. The Dairy CRC no longer does GM cow research, but scientists in New Zealand have produced GM cows that produce high-protein milk for the cheese industry.
High-protein milk is one of only many potential uses for GM cows. In the United States, for example, human medicines are already being produced in the milk of cows and goats. The technology could also be used to produce healthier animals with improved resistance to diseases.
Cooperative Research Centre for Innovative Dairy Products: www.dairycrc.com
SARDI: www.sardi.sa.gov.au