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A2 Cloning animals
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A2 Cloning animals

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A2 OCR syllabus specific on cloning animals and transgenic animals

A2 OCR syllabus specific on cloning animals and transgenic animals

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  • 1. Cloning Animals Creating genetically identical offspring
  • 2. Embryo splitting- artificial identical twins In this simple form a ram with desirable genes is selected (e.g. long coat) The ewe with desirable characteristics is also chosen the egg and sperm are fertilized in vitro The zygote is allowed to grow in vitro to 16 cells then split. The cell bundle can be split in two or more and implanted into one or several surrogate mothers.
  • 3. Artificial cloning of animals (nuclear transfer) The most popular method involves removing the nucleus from the body cell of your animal to be cloned (usually a mammary cell) Take an egg (ovum) of the same species and remove its nucleus (enucleation)
  • 4. Artificial cloning of mammals Insert the genetic information (nucleus) from the body cell into the ovum (electro fusion) Implant the ovum into the oviduct of a surrogate female female to culture Implant the early embryo into a final surrogate mother Await birth!
  • 5. Nuclear transfer method - summary In this the mammary cells are removed from the desired clone sheep An egg cell (ovum) from another sheep is enucleated The mammary nucleus is implanted into the enucleated egg by electro fusion This egg is ‘cultured’ in the oviduct of another sheep and finally implanted into the uterus of a fourth It took 277 attempts!
  • 6. Nuclear transfer - using an ovum/oocyte. The oocyte had to be enucleated to remove the unwanted genetic material so only the ‘clone’ DNA would be replicated. The oocyte is large with extra nutrients to enable development. It is specialized for reproduction and will begin to divide spontaneously and implant in the uterus. These totipotent cells have the capability of turning on any gene in the genome.                                      .
  • 7. Embryo splitting This is a simpler method. Sperm and egg are selected. They are fertilized in vitro The zygote divides to a 16 cell embryo, This is split into four or more, These are implanted into 4 surrogate mothers.
  • 8. Advantages of cloning animals There are hundreds of cloned animals round the world. Desirable trait beasts (e.g. leanest for meat good milkers) can be copied exactly with no variation Endangered species can be copied. Animals altered for pharmaceutical purposes can be copied.
  • 9. Use of cloning to treat disease- Neutrophils in the lungs During a lung infection it is necessary for white blood cells to get into the lungs This is achieved by the white blood cells producing elastase to digest little holes in the alveoli
  • 10. Alpha Anti-trypsin AAT is manufactured by the walls of the alveoli to prevent the further breakdown of the elastin by the White Blood Cells. In humans incapable of producing AAT a series of lung infections can seriously weaken the lungs
  • 11. Loss of elasticity While inspiration is unaffected, expiration and so removal of carbon dioxide becomes less efficient This can lead to hyperventilation and feelings of suffocation It is similar in nature to emphysema
  • 12. How to treat the problem Administering Alpha Anti-trypsin is an effective treatment to prevent this elastin breakdown Currently the main source of AAT is from blood donations
  • 13. milk Tracey the sheep. An egg from a ewe was fertilized with a sperm from a ram in vitro. A plasmid containing the human gene for AAT production was then inserted into the egg using a micropipette The zygote was transferred back to the mother’s womb After many attempts the world’s first transgenic ewe (Tracey) was born Tracey (transgenic ewe)
  • 14. The success of transgenic ewes Tracey produces 35g of AAT in every litre of milk which is an enormous amount. The genes for making AAT were passed to some of her ewe lambs A mere 2000 ewes like Tracey would produce enough milk to supply all the hospitals in the world.
  • 15. Disadvantages of cloning Dolly the sheep died of lung cancer (the initial report of premature ageing was wrong) It is still unclear whether cloning animals with older genetic material is detrimental to the health of the clone It is costly – low success rate expensive technology A clone flock (genetic uniformity)would soon be wiped out by a disease to which their genetic type was susceptible
  • 16. Non-reproductive cloning Also known as therapeutic cloning. Biotechnology has already enabled Biologists to artificially produce simple organs such as bladders to replace those removed due to bladder cancer. Using the individual’s own cells to produce new organs eliminates the problem of rejection.