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Clones

Clones

  • 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

  1. The removal of the diploid nucleus from a body cell (sheep 1)
  2. Enucleation of egg cell (removal of nucleus) (sheep 2)
  3. Insertion of diploid nucleus into enucleated egg cell.
  4. Electrical stimulation of the diploid nucleus to divide by mitosis.
  5. Implantation of embryo into surrogate mammal. (sheep 3)
  6. 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.