animal cloning

• clone 


  a monozygotic twin (genetically identical)
• stem cells from an amnia embryo are 'totipotent' so are capable of differentiation into any cell type and can switch on any of the genes in the genome
• artificial embryo twinning 


  embryo transplant
• somatic cell nuclear transplant 


  cell cloning
• artificial embryo twinning doesn't definitely produce clones with desired characteristics as the first step is genetic combination so you don't know how genes interact. can pick the desired characteristics in the parents but won't 100% have them
• • Animal clones can be produced naturally as a result of sexual reproduction.
  • During sexual reproduction, once an egg has been fertilised, it's possible for it to split during the very early stages of development and develop into multiple embryos with the same genetic information
  • The embryos can develop as normal to produce offspring that are all genetically identical - they are clones. For example, identical twins are natural clones.
• Artificial embryo twinning


  Process of creating genetically identical offspring from a single fertilised egg
• Artificial embryo twinning


  1. Egg cell extracted from female cow

  2. Egg cell fertilised in Petri dish

  3. Fertilised egg left to divide at least once, forming embryo in vitro

  4. Individual cells from embryo separated and put in separate Petri dishes

  5. Cells divide and develop normally, forming embryos in each Petri dish

  6. Embryos implanted into female cows as surrogate mothers

  7. Embryos continue to develop inside surrogate cows

  8. Offspring born, all genetically identical
• The offspring produced through artificial embryo twinning are all genetically identical to each other
• Somatic cell


  Any cell that isn't a reproductive cell
• Somatic cell nuclear transfer

  1. Somatic cell taken from sheep A

  2. Nucleus extracted and kept

  3. Oocyte (immature egg cell) taken from sheep B

  4. Nucleus removed to form enucleated oocyte

  5. Nucleus from sheep A inserted into enucleated oocyte

  6. Nucleus and enucleated oocyte fused and stimulated to divide

  7. Embryo implanted into surrogate mother

  8. Lamb born that's a clone of sheep A
• Uses of animal cloning

  • Research purposes
  • Testing new drugs on cloned animals as they're all genetically identical
  • Increasing the number of animals with desirable characteristics to breed from in agriculture
  • Producing lots of identical animals that all produce the same useful substance
  • Saving endangered animals from extinction by cloning new individuals
• • Cloning doesn't have to be used to make whole animals
  • Sometimes scientists only want the cloned embryonic stem cells
  • These cells are harvested from young embryos and have the potential to become any cell type, so scientists think they could be used to replace damaged tissues in a range of diseases, e.g. heart disease, spinal cord injuries, Parkinson's disease.
  • If replacement tissue is made from cloned embryonic stem cells that are genetically identical to the patient's own cells, it won't be rejected by their immune system.
• Arguments for animal cloning

  • Animals can be cloned at any time - you wouldn't have to wait until a breeding season to get new animals
  • Desirable genetic characteristics are always passed on to clones (e.g. high milk production in cows)
  • Increasing the population of endangered species helps to preserve biodiversity
  • Cloning can help us develop new treatments for disease, which could mean less suffering for some people
  • Infertile animals can be reproduced, so if a farmer's prize winning cow was infertile for any reason, they could still reproduce it
• Desirable genetic characteristics are always passed on to clones (e.g. high milk production in cows)
• This doesn't always happen with sexual reproduction because of processes such as independent assortment and crossing-over, which generate genetic variation during meiosis
• If a farmer had a cow that produced a lot of milk, the only way he could guarantee that his calves would also produce a lot of milk would be to clone the cow
• Arguments against animal cloning

  • Animal cloning is very difficult, time-consuming and expensive
  • There's no genetic variability in cloned populations, so undesirable genetic characteristics (e.g. a weak immune system) are always passed on to clones. This means that all of the cloned animals in a population are susceptible to the same diseases. Potentially, a single disease could wipe them all out
  • Some evidence suggests that clones may not live as long as natural offspring. Some think this is unethical
  • Using cloned human embryos as a source of stem cells is controversial. The embryos are usually destroyed after the embryonic stem cells have been harvested - some people believe that doing this is destroying a human life