Cloning is the process of generating a genetically identical copy of a cell or an organism. Cloning happens all the time in nature—for example in prokaryotic organisms (organisms which lack a cell nucleus), such as bacteria and yeasts, create genetically identical duplicates of themselves using binary fission or budding. Here a cell replicates itself asexually without any genetic alteration or recombination. Natural clones, also known as identical twins, occur in humans and other mammals. These twins are produced when a fertilized egg splits, creating two or more embryos that carry almost identical DNA. Identical twins have nearly the same genetic makeup as each other, but they are genetically different from either parent.
Dolly the Sheep
Dolly, the sheep was the first mammal to be cloned from an adult cell. Scientists working at the Roslin Institute in Scotland produced Dolly, the only lamb born from 277 attempts. Several clones were generated before Dolly, but Dolly was the first mammal to be cloned from an adult cell. For the process of how Dolly was cloned, follow the given links.
Advantages and disadvantages of cloning
Reproductive cloning may enable researchers to make copies of animals with the potential benefits for the fields of medicine and agriculture.For instance, the Scottish researchers who cloned Dolly have cloned other sheep that have been genetically modified to produce milk that contains a human protein essential for blood clotting. The hope is that someday this protein can be purified from the milk and given to humans whose blood does not clot properly.
On the other hand reproductive cloning is a very inefficient technique as most of the cloned animal embryos cannot develop into healthy individuals. For example, Dolly was the only clone to be born live out of a total of 277 cloned embryos. For some other advantages and disadvantages of cloning follow the given link.