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Snippets From Science

• Today scientists can map and count the number of genes in the DNA of plants and animals, and it comes as a surprise that the number of genes doesn’t necessarily reflect the organism’s complexity. Grapes have 30,400 genes, chickens have 16,700 genes, and poplar trees have 40,000 genes. Although we may consider humans to be the most complex of animals, how come we have about 25,000 genes?

In 1990, before techniques for gene mapping were invented, scientists guessed that human DNA had about 100,000 genes. Now we learn that, in terms of number, we lie about halfway between a chicken and grape. The role of genes is to code for specific proteins, which are major life-creating molecules. At one time it was thought that one gene coded for one protein, but today we know that one gene can code for several different proteins. All this serves to amplify the coding possibilities of our 25,000 genes, which, by the way, is the same number of genes found in watercress. (Tina Saey in Science News, Nov. 6, 2010; RefSeq database at the U.S. National Institutes of Health; Pertea and Salzberg, Genome Biology, 2010; http://www.tech.org/genetics, from Stanford University)

• Although it briefly lands on water to feed and returns to terra firma to breed, an albatross spends most of its life at sea, hundreds of miles from land. With a wingspan of about 10 feet, it soars just above the waves without flapping its narrow wings. Recent research suggests that 80-90 percent of the bird’s “wind energy” is provided by taking advantage of the upward movement of air from the crest of waves. The albatross swoops upwind in a zigzag pattern, then rises from the still air in the trough of the wave to catch the gust of wind at the crest. It can also soar along the crest of a wave, lifted by the updraft from the wave’s face. (Science, Nov. 5, 2010; observations of oceanographer Philip Richardson)

• A commonly seen soaring bird in Door County is the Turkey Vulture. Its short, broad wings produce quite a bit of resistance to airflow, but the bird alleviates this resistance by extending and spreading its primary feathers, producing slots between them. These are best seen at the wing tips. Each primary feather functions as a high-aspect-ratio wing (i.e., the ratio of length to width), which reduces wingtip turbulence and lowers stall speed (the minimum speed an aerodynamic object must maintain before it falls from the air). The vulture’s primary feathers help it to circle in thermal air, gliding downward to maintain thrust, and then rising again as it catches the next thermal. (www/stanfordbirds/text/essays/soaring)

• In the recent past, it was supposed that psychiatric medications affected males and females the same way. But about 10 years ago Susan Kornstein, a psychiatrist at Virginia Commonwealth University, showed that women respond much better than men to antidepressant drugs such as Prozac, Zoloft, and Lexapro, which are designed to increase the effectiveness of the neurotransmitter serotonin. These drugs are known as “Selective Serotonin Reuptake Inhibitors,” or SSRIs.

In order to rule out the effect of the menstrual cycle on drug metabolism, the clinical trials that convinced the FDA to approve this class of drugs were conducted on men only. Now it’s known that these drugs work much better in the presence of estrogen, the major female hormone. Men respond better to the antidepressants Tofranil (imipramine) and Wellbutrin (buproprion), which target the neurotransmitters dopamine and norepinephrine. The biomedical community is becoming increasingly concerned about gender differences in the effects of prescription drugs, as well as effects of a given drug on young and old individuals. (Scientific American Mind, May/June 2010)