cloning in animals

• • A clone is a genetically identical copy of another organism.
  • Clones occur naturally in animals through monozygotic twins
• In invertebrates cloning can occur to produce new offspring through fragmentation and regeneration
• Many animals can regrow lost limbs. Whilst this is asexual reproduction of body parts through mitosis it is not classed as cloning because a new organism is not produced.
• • The silvery salamander can clone itself through parthenogenesis.
  • This is where a female grows an embryo without fertilisation occurring.
  • The silvery salamander actually practices gynogenesis or kleptogenesis which is also called sperm parasitism
  • It combines the worst traits of asexual and sexual reproduction and so scientists don’t know why it exists.
• • There are examples of parthenogenesis in all animals except mammals though fish, reptiles and amphibians usually display gynogenesis (often considered incomplete parthenogenesis)
  • They are often rare and usually facultative (meaning it only happens in particular situations e.g. in zoos where there are no males to mate with)
• Artificial animal clones can be produced by

  • Artificial embryo twinning
  • Enucleation and somatic cell transfer
• artificial embryo twinning -

  1. A cow with desirable traits is given fertility hormones to make her ovulate more.
  2. Eggs are fertilised either naturally, artificially inseminated or extracted and fertilised in vitro.
  3. The embryo is split whilst cells are still totipotent.
  4. Embryos are implanted into separate surrogate mothers meaning multiple clones of the original animal will be produced
• Enucleation and somatic cell transfer -

  1. a somatic cell is taken from the animal to be clones, and an unfertilised egg from an egg donor female
  2. an electric current is applied to fuse the empty egg with the donor egg
  3. the nucleus to be cloned is extracted by suction and the egg is enucleated by suction
  4. the embryo matures for 3-6 days
  5. the embryo is implanted into a surrogate mothers uterus
  6. the surrogate gives birth to a cloned animal with identical DNA to the original animal
• Examples in agriculture

  • Produce organisms which mature quickly, produce good meat, produce high yields, are pest resistant, are flood resistant.
  • The farmer might use cloning to aid a selective breeding programme.
  • Increase numbers of organisms with desirable alleles/ traits.
• Examples in medicine

  • Therapeutic cloning is where organs/tissues are grown in a lab to replace damaged or diseased organs in patients.
  • The benefit here is that transplants are genetically identical to the recipient meaning it won’t be rejected by the immune system
• The issue of longevity of cloned animals

  • Cloned animals have more health problems and don’t live as long.
  • The technology is simple in theory but challenging to implement in practice.