Cloning it is a form of asexual reproduction that aims to produce beings with identical physical and biological characteristics, perpetuating genetic characteristics.
The word "cloning" comes from the Greek klon, which means "bud of a vegetable".
Cloning can happen in a way Natural (vegetables, protozoa and fungi) or induced. The latter can be done in 3 steps:
- The nucleus of a somatic cell of the organism that you want to clone is removed (p. ex. a sheep) and this nucleus, which contains all the genetic information of the organism, is transferred to an egg from which the original nucleus has been removed;
- The egg is subjected to the action of certain chemical substances or electrical shocks that stimulate the division process, thus initiating the embryonic development process;
- The embryo is implanted in the uterus of another sheep, which will continue the pregnancy. The being obtained will be a clone and will have the same genetic characteristics as the cloned cell donor.
The first animal to be cloned was a frog, in 1952. In 1997, Ian Wilmut, at the Roslin Institute in Scotland, cloned the first mammal: the Dolly sheep.
In 1998 James Rohl and Steven Stice cloned 2 calves using fetal cells containing a human gene. In 1999, through a new technique of artificial production of twins, Tetra is born, the only survivor of a pregnancy of four monkey clones.
human cloning
In humans, the single-egg twins they are natural clones, that is, they share the same DNA, although some authors disagree with this definition, claiming that for this the twins should be identical to their parents.
Twins have identical genome and similar physical appearance, although the structure and nervous connection of the brain, the structure of the immune systems, the psychic personality and the psychological influence of the environment are many different.
Reproductive Human Cloning
Reproductive human cloning is a technique that makes it possible to create a human being genetically identical to an existing individual.
One of the goals of therapeutic cloning would be to avoid rejection if the donor is the person himself, as for example in the reconstitution of the marrow of an individual who has become paraplegic or in tissue replacement cardiac.
However, human cloning has some delicate aspects, as it does not guarantee development normal, with an anticipated aging, a high rate of perinatal mortality and deficiency in the system immune.