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Process of Cloning

The most common cloning method, known as "somatic cell nuclear transfer" or simply "nuclear transfer," requires two kinds of cell.  One is a somatic cell, which is collected from the animal that is to be cloned (known as the "genetic donor").  A somatic cell is any cell other than a sperm cell or egg cell, and contains the complete DNA, or genetic blueprint, of the animal it came from.  For cloning purposes, somatic cells are typically obtained by a routine skin biopsy performed by a veterinarian.

The other kind of cell required for cloning is an egg cell, which is collected from a female of the same species (known as the "egg donor").  In the lab, a scientist extracts and discards the nucleus of the egg cell, which is the part of the cell that contains the egg donor's genes.  The scientist then inserts the somatic cell from the genetic donor into the egg and "fuses" the two with electricity. The resulting fused egg contains the genetic donor's DNA.

The scientist stimulates the fused egg, which "activates" the egg and causes it to divide just as an egg would if it had been fertilized by a sperm cell in conventional reproduction.  The activated egg is then placed in a culture medium.  As cellular division continues over the course of several days, a blastocyst (early-stage embryo) forms.  After about a week, an embryo transfer specialist transfers the blastocyst to a recipient female (sometimes referred to as "surrogate mother") where it continues to develop.  After a full-term pregnancy, the recipient gives birth to an animal that is essentially the identical twin of the genetic donor.

Egg being prepared for cloning.

  • For an animated walk through the cloning process, click here.