Somatic cells are all the cells that make up an organism except for the germ cells. Germ cells are the sexually reproductive cells, for example the egg and sperm in mammals, including humans. Even though somatic cells can differ throughout an organism, they all contain the same DNA. Germ cells contain half the amount of DNA that is found in the somatic cells.

Somatic cells are thus named based on the Greek term soma. In Greek, soma means body. Every cell type in an organism’s body, except the reproductive cells, is a somatic cell. More simply put, a somatic cell is a non-sex cell.

In humans, somatic cells contain 46 chromosomes or 23 homologous pairs of chromosomes. A homologous pair of chromosomes contains the same genes in the same location, even if the genes are for different conditions of the characteristic they code for. Sex cells only contain 23 chromosomes, or a single copy of each pair. During fertilization, the egg and sperm cell fuse to create a zygote, which will have the full complement of 46 chromosomes. The zygote has one set of 23 chromosomes from the mother and one from the father.

One method of creating clones in mammals uses the nucleus of a somatic cell so that fertilization is not required. During somatic cell nuclear transfer, the nucleus of a somatic cell is removed and the rest of the cell is discarded. The nucleus is the most important part of the cell as it contains all the genetic information for that organism. Any somatic cell can be used for this cloning method, but usually, skin cells are used.

Once the nucleus has been removed from the somatic cell, it is then injected into an egg cell, or ovum, of the same species. Prior to injecting the nucleus into the ovum, the genetic material was removed from it. The ovum no longer needs to be fertilized by a sperm cell as it contains the correct amount of DNA, instead of just half the amount. The ovum containing the somatic cell nucleus can now be implanted into the uterus of a female of the same species so that it can develop.

When the animal has developed fully in the uterus and is born, it will be genetically identical to the original organism, the one where the nucleus was taken from. This cloning technique is far from being perfect. One successful example was the creation of Dolly the sheep in 1996 at the Roslin Institute in Edinburgh, Scotland.