“Full Stem Ahead” (SN: 4/2/05, p. 218) showed several reasons why stem cell research is a good thing: Stem cells from embryos might cure cancer, Parkinson’s disease, Alzheimer’s disease, diabetes, and many other diseases. But the article should have included the fact that stem cells may help with transplanting organs. Stem cells may be used to “grow” organs for patients in need.
Heidi L. Clark
Natrona Heights, Pa.
“Code of Many Colors: Can researchers see race in the genome?” (SN: 4/9/05, p. 232) gives a simplistic and generally inaccurate account of the relationship between Fst [also called Wright’s F statistic] and race/subspecies/species. Fst reflects the relative amount of total genetic variation between populations. While there is bound to be a correlation between Fst and species status, Fst is not normally used to define species. An Fst can be lower between populations of North American grey wolves and coyotes, two different species, than between many populations of the same species, including humans, depending on which genetic loci are considered.
Port Angeles, Wash.
Researcher Sarah Tishkoff of the University of Maryland in College Park, a source for the article, agrees that Fst is not a good indicator of subspecies. She also says the article misrepresented Fst, or Wright’s F statistic, in that an Fst of 15 percent does not mean that two populations differ in 15 percent of their genome. She adds, however, that the story is accurate in saying that the genetic variability between races is much less than that between subspecies in other animals.—C. Brownlee
Research results on the physiological effects of blue light 1.5 hours before bedtime (“Blue light keeps night owls going,” SN: 4/16/05, p. 253) makes me wonder about the effects on sleep and, subsequently, mood and metabolism for the millions of us who spend hours each night staring into two sources of blue light, the television and the computer screen.