Cloning methods in animals

People may want to clone an animal. They may even want to clone a human body part for transplant surgery. Just like the cloning of plants, the cloning of animals has many important commercial implications. It allows an individual animal with desirable features, such as a cow that produces a lot of milk, to be duplicated several times. But the process takes much longer than it does with plants.

Embryo transplants

A developing embryo is removed from a pregnant animal at an early stage, before the embryo's cells have had time to become specialised. The cells are separated, grown for a while in a laboratory, and then transplanted into host mothers.

When the offspring [offspring: A new human, animal or plant that is created as a result of reproduction. ] are born, they are identical to each other and to the original pregnant animal. They are not identical to their host mothers, because they contain different genetic information.

Fusion cell cloning

Fusion cell cloning involves replacing the nucleus [nucleus: The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. ] of an unfertilised egg with the nucleus from a different cell. The replacement nucleus can come from an embryo, but if it comes from an adult cell, it is called adult cell cloning.

Dolly the sheep was the first mammal to be cloned using adult cell cloning. She was born in the UK in 1996 and died in 2003. Here's how she was produced:

1. An egg cell was removed from the ovary [ovary: One of the pair of organs (ovaries) in the female reproductive system where eggs (ova) and sex hormones are produced. ] of an adult female sheep, and its nucleus removed.
2. The nucleus from an udder cell of a donor sheep was inserted into the empty egg cell.
3. The fused cell then began to develop normally, using genetic information from the donated DNA [DNA: The material inside the nucleus of cells, carrying genetic information. DNA stands for Deoxyribonucleic Acid. ].
4. Before the dividing cells became specialised, the embryo was implanted into the uterus [uterus: Also known as a womb. This is where the fertilised egg (ovum) develops. ] of a foster mother sheep. The result was Dolly, genetically identical to the donor sheep.

The cloning process of 'Dolly the sheep'

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