Monday, November 24, 2008

Re-creating Extinct Animals

According to a recent article in the New York Times, advances in DNA sequencing and genetic engineering techniques are leading to cautious optimism among scientists that someday it may be possible to bring extinct animals back to life. But it will not be easy. DNA undergoes decay after death, falling apart into little pieces within about 60,000 years. Determining the correct sequence of an extinct species’ DNA requires special DNA sequencers that can analyze the tiny pieces and then calculate how they were aligned in the original intact molecule.

The second step would be to actually reconstruct the deciphered DNA code back into intact DNA once again. One way would be to “reverse engineer” the DNA of a close living relative species until it is similar to the known sequence of the extinct species. So far this has not been possible because of the sheer numbers of base pairs (perhaps half a million) that would need to be modified. But researchers are hopeful that techniques will be available soon to modify up to 50,000 sites at a time. The extinct species’ DNA would then be inserted into an egg of the living relative and incubated in that relative until birth.

How would your students react if it were to be announced one day that an extinct human such as a Neanderthal had been reverse engineered and then born to a modern human or a primate mother?!

Thursday, November 20, 2008

Ginkgo Doesn't Prevent Dementia

According to a study in the Journal of the American Medical Association, daily doses of the popular herbal antioxidant Ginkgo biloba neither prevent nor delay the onset of dementia (cognitive impairment). The most common type of dementia is Alzheimer’s disease.

Herbal extracts of Ginkgo remain popular as a memory enhancer, even though previous scientific evidence showed that Ginkgo just doesn’t enhance memory. So don't expect this latest finding regarding dementia to put much of a dent in Ginkgo’s annual sales of over $200 million. Good marketing apparently trumps good science.

Thursday, November 13, 2008

Surrogate Grandmother

According to an Associated Press article that appeared in many major newspapers and news services yesterday, a 56-year-old woman gave birth last month to triplets. The event was noteworthy because the three baby girls were actually her biological granddaughters.

Apparently a young couple could not conceive because the woman had had a hysterectomy. So they used in vitro fertilization (IVF) to produce their embryos, which were then implanted into the young woman’s 56-year-old mother.

My class took quite an interest in the many and varied reproductive possibilities raised by modern IVF techniques. They understood the obvious benefit, which is to enable some infertile couples to have children of their own. They also quickly grasped that it could also be used (in combination with preimplantation genetic diagnosis) to choose a child’s sex, to avoid having a child with certain genetic disorders, or even to cure an older sibling of a genetic disorder (See the Current Issue in Human Biology 5th ed., pp. 396-397). But they didn’t come up with this scenario!

Tuesday, November 11, 2008

Whatever Happened to Golden Rice?

Golden rice was once heralded as a cure for vitamin A deficiency, which kills or blinds children in poorer countries worldwide. But twelve years after its development golden rice is still not being produced and distributed. The primary reason is categorical opposition to all genetically engineered (GE) foods by organizations such as Greenpeace. Greenpeace argues that although golden rice might indeed benefit vitamin-deficient children, acceptance of golden rice would open the door to other GE crops that Greenpeace vehemently opposes.

In the face of intense, well-organized opposition, government regulatory agencies have been reluctant to approve GE crops, including golden rice. The company holding the patent on golden rice eventually gave up, saying there was no money in it. It's still being studied in a few labs by humanitarian organizations such as World Food Day, but don’t expect to see it on grocery shelves any time soon. That's too bad, for golden rice really is a product that could help people in need, as opposed to just helping food producers and manufacturers.

Sunday, November 2, 2008

New Nutrient Standards for Packaged Foods

Finally, someone has decided to make it easy for consumers to pick the healthiest packaged foods! A coalition of some of the biggest food companies has teamed up with scientists and the federal government to develop and promote a simple front-of-package logo called “Smart Choices” to indicate that a food meets certain nutritional standards. The standards include limited quantities of total and saturated fats, cholesterol, added sugars and salt, as well as minimum quantities of nutrients for good health, such as calcium, potassium, fiber, and certain vitamins. And like the “Heart Healthy” program originally developed by the American Heart Association, the new program is based on good scientific evidence.

Once consumers understand what the logo means and accept its underlying health assumptions, they can simply look for the logo on the front of the package. “Pattern recognizers” such as myself (who can’t find their favorite products in the grocery store if the manufacturer changes the packaging!) will appreciate the help in picking healthful foods. The logo is a green check mark in a square along with the words, “Smart Choices Program”. For a complete listing of the nutritional requirements to earn the Smart Choices label, visit the Smart Choices website. The logo should begin appearing on products in stores by the middle of next year.