The announcement that a 35-year-old woman is hoping to give birth to the world’s first cloned baby turned the spotlight once again on a highly controversial process that has divided scientists, politicians and the public.
Q: What is cloning?
A: Cloning is the process of making a genetically identical organism without normal sexual means.
Practically, cloning means the creation of cells or even whole plants or animals using DNA from a single “parent” – bypassing the normal reproductive process.
Clones do occur naturally, such as in identical human twins, which although they are genetically different from their parents, they are naturally occurring clones of each other.
The advent of human cloning has aroused worldwide interest and concern because of its scientific and ethical implications.
Critics say it is “playing God”, while scientists caution that most mammal clones do not even make it to birth or are born with abnormalities.
Others say cloning is an inevitable result of advances in science and technology.
Q: When did cloning begin?
A: Animal cloning has been the subject of scientific experiments for years, but received little attention until the birth of the first cloned mammal in 1997.
The much-celebrated Dolly the sheep was created by scientists at the Roslin Institute in Edinburgh.
Since Dolly, several scientists have cloned other animals, including cows, mice and pigs.
A projects was even launched to clone a prehistoric woolly mammoth in Japan.
Scientists knew the technology used to produce Dolly could also be used to clone a human.
But the recent success in cloning animals has sparked fierce debates about the use and morality of cloning plants, animals and possibly humans.
Q: How does cloning animals or humans work?
A: Cloning is an umbrella term used by scientists to describe a number of different processes for duplicating biological material.
Blastomere separation (sometimes called twinning after the naturally occurring process that creates identical twins) involves splitting a developing embryo soon after fertilisation of the egg by a sperm (sexual reproduction) to give rise to two or more embryos.
The resulting organisms are identical twins (clones) containing DNA from both the mother and the father.
Before making his shock announcement today, Dr Panos Zavos unveiled plans to seek a woman prepared to receive a split embryo, half of which would be used for “spare part” surgery.
Dolly, on the other hand, was the result of another type of cloning called nuclear transfer which produces an animal carrying the DNA of only one parent.
This takes DNA from one adult cell and puts it into a “hollowed out” egg.
Chemicals and electricity are then used to encourage the new DNA to fuse with the egg and develop into an embryo.
Scientists at the Roslin Institute transplanted a nucleus from a mammary gland cell of one sheep into the egg of another.
The nucleus-egg was stimulated with electricity to fuse and encourage growth.
Dolly was born months later and shown to be genetically identical to the original cells and not the “mother” she had been born from – demonstrating she was a clone.
Q: Why clone?
A: The function of cloning plants or animals is to mass produce organisms with desired qualities.
The reasons for cloning are many – from producing award-wining orchids to re-creating animals or humans to counter disease and illness.
Sheep have been genetically engineered to produce human insulin, which natural breeding may not produce.
Cloning could also create perfect-match tissue. Currently if humans have an organ transplant the body can reject the donated cells as foreign bodies.
But cells created through “therapeutic cloning” would not be rejected because the new cells would be derived from the patient so his or her immune system would not react.
For leukaemia patients needing the right bone marrow donors, doctors could create perfectly matched bone marrow using the patient’s own skin cells.
Other reasons for cloning might include replacing lost or deceased family pets and repopulating endangered or even extinct species.
But scientists remain uncertain about the future long term health prospects of genetically cloned animals – or humans.