cloning in animals

• what is natural cloning in animals referred to as?

  • natural twinning
  • formation of monozygotic twins by embryonic twinning
• what are the two artificial ways of producing twins in animals?

  • artificial twinning
  • SCNT (Somatic cell nuclear transfer)
• what is artificial twinning used for?

  in farming- to produce the maximum offspring for good diary/beef
• state the process of artificial twinning

  • cow with desirable characteristics is treated with hormones so she super-ovulates and produces more ova than normal
  • ova can be fertilised naturally or by artificial insemination
  • ova flushed out of the uterus
  • alternatively, ova can be extracted and fertilised by bull's semen in vitro
  • when cells still totipotent, embryos split to produce smaller embryos, all of which are totipotent
  • each embryo is implanted into surrogate mother as single pregnancies carry fewer risks
  • all the offspring are genetically identical to each other
• what is an enucleated egg?

  An egg cell from which the nucleus has been removed.
• describe the process of SCNT

  • nucleus removed from a somatic adult animal cell
  • nucleus removed from the ovum of a different female animal of the same species
  • nucleus placed into enucleated ovum, given electric shock so it fuses and begins to divide
  • or somatic cell placed next to the enucleated ovum and fuses using an electric current (electrofusion)
  • embryo that develops transferred to uterus of third animal where it develops (so three animals are involved in this process)
  • The animal is a clone of the original animal from which the somatic cell was derived from
• in SCNT, why might the clone produced not be exactly fully genetically identical to the original mother?

  the enucleated ovum will contain the mt DNA whoch will be present in the clone
• what is SCNT also referred to as?

  • reproductive cloning
  • as live animals are the end result
• what are the advantages of animal cloning?

  • artificial twinning produces more offspring that natural twinning
  • artificial twinning enables the success of a male at passing on desirable genes to be determined- can be used to produce more clones if first clone is successful
  • SCNT has been used to clone domestic pets/racehorses
  • SCNT allows extinct animals to be reproduced
• what are the disadvantages of artificial cloning?

  • inefficient- requires many eggs to produce a single cloned offspring
  • cloned animal embryos fail to develop and often miscarry or produced malformed offspring
  • animals produced by cloning have shortened lifespans
  • SCNT has been relatively unsuccessful in increasing the populations of rare species