- Clones are individuals which are genetically identical. Making plant clones – bit of leaf, stem or root is planted to form a clone of the original plant – is far easier than cloning animals.
- Clone: These are individuals that genetically identical.
Stages in the production of cloned mammals
- The removal of the diploid nucleus from a body cell (sheep 1)
- Enucleation of egg cell (removal of nucleus) (sheep 2)
- Insertion of diploid nucleus into enucleated egg cell.
- Electrical stimulation of the diploid nucleus to divide by mitosis.
- Implantation of embryo into surrogate mammal. (sheep 3)
- The offspring born by the surrogate mammal is a clone of sheep 1 not sheep 2.
- Making plant clones can be relatively easy; you start with a bit of leaf, stem or root of the original plant. The plant cells divide and produce new cells, which grow into a clone of the original plant. This is an example of asexual reproduction.
Advantages of cloning
- Cloning mammals could help with the shortage of organs for transplants. For example, genetically-modified pigs are being bred that could provide suitable organs for humans. If this is successful, then cloning these pigs could help meet the demand for organ transplants.
- The study of animal clones could mean a greater understanding of embryos, ageing and age related disorders.
- Cloning could be used to preserve an endangered species.
Disadvantages of cloning
- Cloning mammals could lead to a reduced gene pool – fewer different alleles in the population:
- If a population are all closely related and a new disease appears, they could all die as none of them may have the allele of resistance to the disease.
- Cloned mammals do not live as long. Dolly the sheep only lived for 6 years which is half as long as many sheep.
- She had lung disease and arthritis and she was put down. These diseases are more common in older sheep.
- She had been cloned from an older sheep, so it may have been her ‘true’ age was older.
- She may have been just unlucky – her illnesses were not linked with her being a clone.
- Other risks and problems:
- Cloning process often fails; it took 237 attempts to clone Dolly.
- Clones are often born with genetic defects.
Cloned mammals’ immune systems are sometimes unhealthy, so they suffer from more diseases.