Somatic cell donorThe animal to be copied. One of its body cells supplies the nucleus, so the clone matches this animal.
Egg donorThe animal that supplies the egg cell. Its chromosomes are removed with the egg's nucleus.
Surrogate motherAn adult female that carries the embryo until birth. She gives the lamb none of her chromosomes.
CloneA genetic copy of the animal that gave the body cell. The first mammal cloned from an adult cell was a lamb born in 1996.
The cells and steps 7
Somatic cell (body cell)Any body cell other than an egg or sperm cell. Its nucleus holds two full sets of chromosomes.
Donor nucleusThe part of the body cell that holds its DNA. It is moved into the empty egg.
Egg cell (oocyte)An unfertilized egg cell, also called an oocyte. Its own nucleus is taken out.
Egg nucleus (removed)The egg cell's own nucleus, with its DNA. It is removed and plays no further part.
Enucleated eggAn egg cell with its nucleus removed. Enucleated means without a nucleus.
Electric current (fusion)It fuses the body cell with the empty egg. The egg then holds the donor nucleus.
Early embryoA dividing ball of cells grown from the egg. Both sets of chromosomes in every cell come from the body cell.
How this list was compiled: Every name and step checked on 2026-10-03 against the US National Human Genome Research Institute, Cloning Fact Sheet (https://www.genome.gov/about-genomics/fact-sheets/Cloning-Fact-Sheet); Wikipedia: Somatic cell nuclear transfer and Dolly (sheep), text only; the University of Utah, Learn.Genetics: What is Cloning; and the Roslin Institute of the University of Edinburgh, The Life of Dolly (archived copy). The names of the two donor animals as labels: Wikipedia and two books read through full-text search, Carrie Friese, Cloning Wild Life (2013), and Aaron D. Levine, Cloning: A Beginner's Guide (2007). Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry; nothing traced. Licence: own work
How it works
Somatic cell nuclear transfer moves the nucleus of a body cell into an egg cell whose own nucleus has been removed. This diagram of somatic cell nuclear transfer follows the steps for a sheep.
Read the full guide
Read the two columns down
On the left, a body cell is taken from the animal to be copied; its nucleus holds that animal's DNA. On the right, an egg cell is taken from another animal and its nucleus is removed, which leaves an enucleated egg. The donor nucleus goes into the empty egg. The bolt marks the electric current that fuses the body cell with the egg.
From egg to lamb
The egg divides into an early embryo, which is placed in a surrogate mother. The lamb she carries is a clone of the animal that gave the body cell, not of the egg donor or the surrogate.
The chart shows the nucleus moving alone; laboratories often fuse the whole body cell with the empty egg.
The egg donor and the surrogate are drawn with horns, so the lamb is seen to match the cell donor.
Questions and answers
What is somatic cell nuclear transfer?
A laboratory method for making a clone. The nucleus of a somatic cell, which is any body cell other than an egg or sperm cell, is moved into an egg cell whose own nucleus has been removed. The egg can then develop into an embryo.
What are the steps of somatic cell nuclear transfer?
A body cell is taken from the animal to be copied. An egg cell's nucleus is removed. The body cell's nucleus goes into the empty egg, often by fusing the cells with an electric current. The embryo that grows is placed in a surrogate mother.
Which animal does the clone match?
The one that gave the body cell, because that cell's nucleus holds the DNA. Both sets of chromosomes in the embryo come from the body cell. The egg donor's nucleus was removed, and the surrogate mother only carries the embryo.
How was Dolly the sheep cloned?
By somatic cell nuclear transfer. A cell from a six-year-old Finn Dorset sheep's mammary gland supplied the nucleus, another sheep supplied the egg cell, and a surrogate mother carried the embryo. Dolly was born on July 5, 1996.