Animals can be cloned using embryo transplants. In this process, the animals are cloned through a method that begins with sexual reproduction. Below is the process for embryo transplants.
1. Egg cells from one animal with desirable traits are artificially fertilised with sperm cells from another animal with desirable traits.
2. Then, the egg is left to develop into an early-stage embryo.
3. The early-stage embryo is divided into multiple embryos before the cells become specialised.
4. This forms many identical embryos, which are transplanted into host mothers, where the embryos will grow and develop.
5. The host mothers will give birth to identical offspring, which are clones of each other.
Animal cloning aims to achieve superior characteristics, but embryo cloning isn’t always the preferred method. Since it starts with a sperm and an egg, there’s no certainty that the offspring will consistently exhibit the desired traits.
The first mammal to be cloned was a sheep called Dolly, in 1996, using adult-cell cloning. An advantage of adult-cell cloning is that we are able to clone animals with desirable traits.
The process of adult-cell cloning:
1. Remove a cell (e.g. a skin cell) from the adult animal.
2. Separate the nucleus from the cell (which contains the genetic information of the cloned animal).
3. Take an unfertilised egg cell from an adult female of the same species and remove the nucleus.
4. Take the nucleus from the original adult cell and insert it into the egg cell.
5. Administer a small electric shock to the egg cell. This stimulates the cell to divide by mitosis, leading to the formation of an embryo.
6. Insert the embryo into a surrogate mother to continue development.
7. When the animal is carried to term, the host mother will give birth to a clone that is genetically identical to the original adult animal.