Cloning is done by removal of DNA from an ovum and replacing it with the DNA of an adult animal. The fertilized ovum is implanted in a womb and an identical or clone animal can be produced. However, the technique is fraught with risks. The cloned animals have been known to carry genetic disorders and have a comparatively short lifespans.
Not many people know that Dolly was not the first animal to have been cloned by scientists. Way back in 1958, scientist John Gurdon claimed to have cloned a frog by using intact nuclei from somatic cells of a Xenopus tadpole. In 1963, Chinese embryologist Tong Dizhou created the first fish clone by inserting the DNA from a male Asian carp into the egg of a female Asian carp. Dizhou went on to create the first interspecies carp clone by inserting Asian carp DNA into a European crucian carp in 1973. In 1986, a mouse named Masha became the first mammal to be cloned using embryo cell.
However, Dolly is still regarded as the most significant achievement in the history of cloning because she was the first mammal to have been cloned using adult cells. Before her, cells extracted from an embryo were being used to create a clone. The success of the Dolly experiment also resulted in a fierce competition among various research groups who started cloning one animal after another.
Scientists at the University of Hawaii created Cumulina, the first mouse clone using adult cells, within one year of Dolly’s birth in 1997.[ad#co-1]
The first cloned calf was also born in the same year and later kept at Minnesota Zoo Education Center. In 1999, Dr Xiangzhong (Jerry) Yang cloned a Holstein heifer named Amy by using ear skin cells from a high-merit cow named Aspen at the University of Connecticut. He followed it up by three additional clones, Betty, Cathy and Daisy in the same year.
The year 1999 saw birth of Second Chance, a Brahman bull which was cloned from a celebrity bull Chance at the Texas A&M University. The research centre was also successful in cloning a Black Angus bull named 86 Squared 15 using cells from his donor, Bull 86, which were frozen in 2000. Just like its parent, the cloned bull also exhibited natural resistance to tuberculosis, brucellosis, and other diseases which can be transmitted to meat.
Five Scottish piglets were created using cloning technique in 2000. In 2001, cloning was done to save Gaur, an endangered species of wild cattle. It was born from a surrogate domestic cow mother at the Trans Ova Genetics in Sioux Center, Iowa, USA. However, the clone died within two days.
The year 2001 saw intensified activity in the field of cloning with birth of two female jersey cows Millie and Emma at the University of Tennessee. They were the first cows to be produced using standard cell-culturing techniques.
In the same year a cat called CopyCat was cloned at Texas A&M University. Though the DNAs of both the clone and the host were same, they had different personalities. Around 10 more Jersey cows were cloned at the University of Tennessee in 2002 while the first commercially cloned cat, Little Nicky, was created by Genetic Savings & Clone in 2004.
In 2003, a Boer goat was cloned at Texas A&M University. In the same year, three male mules were cloned for the first time while a rabbit was also cloned in France.
The year also saw the birth of a first cloned deer named Dewey at Texas A&M University while in 2005 South Korean scientist Hwang Woo-Suk cloned the first dog, Snuppy, an afghan hound. South Korean scientists went on to clone sniffer dogs.
Anatolian Grey bull called Efe was cloned in Turkey along with world’s first buffalo calf through the “hand guided cloning technique” in the year 2009. Next year, the first Spanish fighting bull was cloned by Spanish scientists.
The cloning experiments on animals are still on around the world while there are some unverified claims of human cloning too.[ad#afterpost]