Biology in the Laboratory
Have any other animals been successfully cloned?
No, contrary to popular science fiction stories, cloned animals do not look like the original donor of the mature cells or their identical clones. As with most people—even human twins—the environment plays an important role in how an organism looks. For example, in 2001, the first cloned cat was born, called Cc, or Carbon Copy or CopyCat—from a genetic donor named Rainbow, but put into a “surrogate mother” that was a female tabby (Cc was the only one of eighty-seven embryos in the experiment that was successful). The resulting cat looks very different from Rainbow or her surrogate mother. This difference is due to the fact that the color and pattern of cat coats are not attributed exclusively to genes, and in this case, the cloning process also “changed” the cat’s color and pattern. In 2006, Cc became the first cloned cat that had ever given birth to kittens.
Dolly is considered to be the first mammal cloned from a mature cell taken from an adult animal, but in 1979, scientists produced the first genetically identical mice by splitting mouse embryos in a test tube. They then implanted the embryos into the wombs of adult female mice with success. After that, the same procedure was used to produce genetically identical cows, sheep, and chickens by transferring the embryos into the wombs of their respective adult female animals.
After the success of Dolly, most animal cloning has used the mature cells from adult animals such as a skin cell or udder cells. Two years after Dolly, Japanese scientists cloned eight calves from a single cow, with only half of them surviving. And since then, other mammals have been cloned in the same way, including cats, deer, dogs, horses, mules, ox, rabbits, and rats.