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MULTIPLICITY
An exploration of cloning adult mammals: Answers to questions about the scientific process by Dr. Neal First, of the University of Wisconsin Dept. of Meat and Animal Science March 10, 1997 |
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For Dr. John Fletcher's answers to questions about the ethics of cloning
click here.
To read Additional Comments from Online NewsHour Visitors
click here.
To return to the Discussion Introduction
click here.
NewsHour Backgrounders
February 24, 1997:
A background report on the cloning of sheep in Scotland.
February 24, 1997:
A technical discussion on the science of genetic engineering.
February 24, 1997:
A discussion on the ethics of genetic engineering and cloning mammals.
April 3, 1996:
Fred De Sam Lazaro reports on scientific advances in genetic research and the ethical questions they raise.
OUTSIDE LINKS
Roslin Institute, Edinburgh, Scotland report on cloning sheep.
The American Association for the Advancement of Science news brief on the Scottish cloning experiment.
The Genetics and Public Issues Program at The National Center for Genome Resources (NCGR) discusses cloning.
Discussion of Ethics and Social Issues in Gene Research at the Human Genome Project.
Browse the University of Pennsylvania Center for Bioethics home page.
Rick Tenney of Lambertville, MI, asks:
Dr. First, I'm wondering about the growth process of Dolly, did she grow normally (first to a lamb and then an adult), or did she just start out growing into an adult sheep?Dr. Neal First responds:
Dolly developed normally post natally and into a young adult. However a mate to the lamb died soon after birth and otherwise was normally developed. Whether the death was related to being a product of cloning is not known.
James E. Shaw of Columbus, OH, asks:
What is it in the cytoplasm of the egg that directs a differentiated adult cell to reset its clock to moments just after conception time? Any ideas as to what is so special in the cytoplasm of the egg that could do this?Dr. Neal First responds:
We do not know exactly how the egg re-sets the clock, but it is known that egg cytoplasm replaces the donor cell cytoplasm with a large number of oocyte proteins and messages to be used later in development. We also know that in the mouse the DNA of the zygote and early embryo becomes poorly methylated under the influence of oocyte derived cytoplasm in the embryo and that methylation patterns then become established again as differentiation events occur.
Pat Kushko of Toronto, Ontario, asks:
I'd like to know if an emybro could be germinated (so-to-speak) with a slightly dissimilar species, e.g. goat's gene with a sheep embryo, and have the sheep carry this to term?
Dr. Neal First responds:
There are a few close species such as goat and sheep where they have carried each other's offspring in utero to term, but in more distantly related species this has not been possible. Also the interesting question of whether the egg cytoplasm of the sheep or cow would re-program the nucleus of another species and develop offspring to term.
Bob Borries of Whittier, CA, asks:
When you clone someone, what gets transfered in the process? Are traits like personality, intellegence and talent passed onto the clone? If so, shouldn't we be preserving DNA samples from great people who contribute to humankind?Dr. Neal First responds:
With cattle, the geneticists studying inheritance of milk production, calculate that about 70 % of the milk production of a clone will be due to its genetic idenity with its clone mate and 30 % will be due to enviromental and experience factors such as different in utero environment, post natal and lactation environments. I would think that issues pertaining to the brain are even more a product of experiences and learning. Clones may also differ in their mitochondria since they are produced in 2 separate oocytes, and even though the donor cells contributed identical mitochondria. As far as has been studied, only to 120 cell stage, the cloned embryo posesses 2 marked sets of mitochondria.
R. Opperman of Wildomar, CA, asks:
Could cloning impact species diversity negatively, if used extensively for commercial reasons? How could this be avoided, so as to avoid extinction?Dr. Neal First responds:
Cloning could impact species diversity in both negative and positive ways. In a negative sense an entire population of clones would have little genetic diversity although some phenotypic diversity. In a positive sense, planned development of separate clonal lines with different characteristics and their use in cross breeding could expand the diversity of a population .This is especially true if rare DNA were increased in frequency by the process. This potential use of clones is looked at as a way of saving endangered species.
For Dr. John Fletcher's answers to questions about the ethics of cloning click here.
To read Additional Comments from Online NewsHour Visitors, click here.
To return to the Discussion Introduction,
click here.
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