State of Science :: Food Safety
Human Genome Sheds Light on Problems with Animal Cloning
The U.S. Food and Drug Administration (FDA) is expected to soon announce approval of animal cloning for a range of applications in livestock agriculture, according to a story in the Washington Post (access the full story below). This decision is bound to raise new scientific concerns and questions in the minds of many consumers.
The "Human Genome Project Information Center" has developed a "Cloning Fact Sheet" that describes how cloning is accomplished and assesses the outcomes of past attempts to clone animals. The "Fact Sheet" contains a sober assessment of the risks entailed in animal cloning.
"Reproductive cloning is expensive and highly inefficient. More than 90% of cloning attempts fail to produce viable offspring. More than 100
nuclear transfer procedures could be required to produce one viable clone. In addition to low success rates, cloned animals tend to have more compromised immune function and higher rates of infection, tumor growth, and other disorders.
Japanese studies have shown that cloned mice live in poor health and die early. About a third of the cloned calves born alive have died young, and many of them were abnormally large. Many cloned animals have not lived long enough to generate good data about how clones age.
Appearing healthy at a young age unfortunately is not a good indicator of long term survival. Clones have been known to die mysteriously. For example, Australia's first cloned sheep appeared healthy and energetic on the day she died, and the results from her autopsy failed to determine a cause of death.
In 2002, researchers at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, reported that the genomes of cloned mice are compromised. In analyzing more than 10,000 liver and placenta cells of cloned mice, they discovered that about 4% of genes
function abnormally. The abnormalities do not arise from mutations in the genes but from changes in the normal activation or expression of
Problems also may result from programming errors in the genetic material from a donor cell. When an embryo is created from the union of a sperm and an egg, the embryo receives copies of most genes from both parents. A process called "imprinting" chemically marks the DNA from the mother and father so that only one copy of a gene (either the maternal or paternal gene) is turned on. Defects in the genetic imprint of DNA from a single donor cell may lead to some of the developmental abnormalities of cloned embryos."
More at: Cloning Risks