Animal Cloning

This lesson covers: 

1. Natural animal cloning
2. Artificial embryo twinning
3. Somatic cell nuclear transfer
4. Applications of animal cloning
5. Arguments for and against the use of animal cloning

Natural animal cloning

Natural cloning occurs when animals produce genetically identical offspring using asexual reproduction.

Natural cloning in invertebrates:

• Some invertebrates undergo regeneration or fragmentation.
• This forms new, genetically identical offspring from parts of their bodies that have broken off.
• e.g. Hydra forms 'buds' that break off the parent organism and grow into new, genetically identical offspring.

Natural cloning in vertebrates:

• This can occur naturally when an early embryo splits into two genetically identical embryos.
• Each embryo grows independently, resulting in genetically identical offspring, known as identical or monozygotic twins.
• e.g. With human identical twins.

Artificial embryo twinning

Artificial embryo twinning is a process in which a single early embryo is manually split, separating its cells before they start to differentiate. This produces multiple identical offspring from a single embryo.

This process of artificial twinning:

1. A female organism is treated with hormones to produce multiple ova (egg cells).
2. The ova are extracted and fertilised in a Petri dish to produce an embryo.
3. The embryo divides into several cells and, while the cells are still totipotent, the embryo is split.
4. Each cell is placed into its own Petri dish to develop into individual embryos.
5. The embryos are implanted into the uteruses of surrogate mothers for development.

The result is the birth of genetically identical animal clones.

Somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is a process in which a nucleus is transferred from a somatic (body) cell of one animal into an ovum of another animal to form an embryo. This process leads to the development of a clone of the organism from which the nucleus was extracted.

Steps in SCNT:

1. A somatic cell nucleus is removed from an adult animal.
2. An ovum of a different female animal of the same species is enucleated (the nucleus is removed).
3. The nucleus from the somatic cell is transferred into the enucleated ovum.
4. The somatic nucleus is fused with the enucleated ovum, often stimulated by an electric shock through electrofusion.
5. The fused cell begins dividing, forming an embryo.
6. This embryo is implanted into the uterus of a surrogate mother.
7. The surrogate eventually gives birth to a clone of the somatic cell donor.

Applications of animal cloning

Animal cloning serves various important purposes.

Some examples of the applications of animal cloning involve:

• Medical research - Cloning produces genetically identical animals for drug testing and disease modelling.
• Conservation - It offers a method to boost the numbers of endangered species from a limited gene pool.
• Agriculture - Cloning can replicate animals with desirable characteristics for selective breeding to improve product quality.
• Pharming - Genetically engineered animal clones can be used to produce therapeutic proteins.
• Stem cells - Cloned embryos provide a source of immunocompatible stem cells for tissue repair.

Arguments for and against animal cloning

The debate over animal cloning technology includes ethical considerations on both sides.