Cloning: Dolly and beyond A. Student University of Pennsylvania April 10, 2000
What was Dolly? • In 1997 Dolly the sheep became the first vertebrate cloned from the cell of an adult animal. Not only was this a remarkable scientific breakthrough but it immediately gained interest and concern from around the world on the future of cloning technology as it would effect humans.
Topics of Discussion • What is cloning? • Methods of cloning • Dolly in detail • Dolly’s probability • Today’s legality • The future of cloning • Ethical final questions
What is cloning? • Reproductive cloning- The entire animal is produced from a single cell by asexual reproduction. This would allow for the creation of a human being who is genetically identical to another. • Therapeutic cloning- Broader use of the term “cloning.” Does not create a new genetically identical individual. Research includes therapy for human mitochondria disease and others that could replace damaged or diseased tissues without the risk of rejecting another’s tissue. Could create new skin tissue for burn patients.
Other types of cloning • Multiple copies of genes or gene fragments, repeating nucleotide sequences • Single cell organisms, like bacteria and fungi. This includes fermentation processes for production of bread, beer, and wine. • Entire plant asexual replication • Natural cloning occurs in sexual reproduction, when the embryo splits in two to produce twins.
Methods of cloning • Embryo splitting- Artificially splitting a single embryo at a very early stage of development. In the natural process this would create twins. However, because this is done at an early stage and there are usually less than eight cells you can only make a few clones. Both the nuclear genes and mitochondria genes would be identical.
Methods of cloning • Nuclear replacement- Genetic material (nucleus from embryonic, fetal, or adult cell) is removed and placed into an unfertilized egg or embryo, whose nucleus has been removed. In this case the nuclear genes remain the same but the mitochondria DNA would be different. This has the potential to create the clone of an adult organism as well as many clones at once.
Dolly in detail • Dolly was cloned using the nuclear replacement method. Again the nucleus with chromosome sets is fused with an unfertilized egg whose nucleus has been removed. • Motivating factor was that it could help to improve certain qualities in livestock. • Dolly was not the first sheep to be created from nuclear replacement. Two genetically identical sheep, Megan and Morag were born in 1996 using the technique. The difference was that Dolly was derived from an adult sheep, and Megan and Morag were from a sheep embryo.
Dolly’s probability • Cells taken from a six-year-old Finnish Dorset ewe and cultured in a lab. • 277 cells then fused with 277 unfertilized eggs (each with the nucleus removed) • 29 viable reconstructed eggs survived and were implanted in surrogate Blackface ewes. • 1 gave birth to Dolly • 0.361% chance at onset, 3.4482% once implanted. In nature between 33-50% of fertilized eggs develop.
Today’s Legality • In Great Britain, clones are allowed to be made and born. Cloning does require a license, and scientists must follow strict guidelines. • 1990 Human Fertilization and Embryology Act allows research on embryos for up to fourteen days. • Most laws state that any embryo that has been researched upon cannot be then placed into a uterus.
Today’s Legality • 1997 House bill prohibited use of federal money for experimentation with cell transfer technology to produce an embryo that is a human clone. Federal rules prohibit federal funding for embryo research. The bill allowed for continuation of federal research on plant and animal cloning. It did not affect research at biotech companies or academic institutions, which don't receive federal funding.
The future of cloning • Research could give insight to origins of cancer and other cellular processes such as aging. • Techniques could be used with nerve cells that do not regularly reproduce. Could possibly help Alzheimer or Parkinson’s sufferers. • Nuclear replacement could help those with diseases that are inherited from mitochondria. The nucleus is removed from the diseased cell and placed into one with healthy mitochondria.
Ethical final questions • Are human clones individuals? • Do clones have parents? Who are they? The cell donor? Nucleus donor? Surrogate? • How old is a clone? Go by age of DNA or age of tissues? • Do the benefits of cloning outweigh possible number of trials (possibly failed ones) that would have to occur with human embryos? • Is it ok to clone for outstanding individuals physically or mentally? For experiments?