How does SCNT differ from the natural way of making an embryo?
The fertilization of an egg by a sperm and the SCNT cloning method both result in the same thing: a dividing ball of cells, called an embryo. So what exactly is the difference between these methods?
An embryo is composed of cells that contain two complete sets of chromosomes. The difference between fertilization and SCNT lies in where those two sets originated.
In fertilization, the sperm and egg both contain one set of chromosomes. When the sperm and egg join, the resulting zygote ends up with two sets - one from the father (sperm) and one from the mother (egg).
In SCNT, the egg cell's single set of chromosomes is removed. It is replaced by the nucleus from a somatic cell, which already contains two complete sets of chromosomes. Therefore, in the resulting embryo, both sets of chromosomes come from the somatic cell.