cle trumpeting a new "genetic link" to a behavior or disease. Everything from schizophrenia to television watching is postulated to be "linked" to genetics, yet scientists are a long way from being able to explain the ramifications of the human genome sequence. Kaye (1992) suggests that phrasing used by the media such as "gene for alcoholism" is misleading: Noble and Blum "had only suggested a possible genetic component contributing indirectly to the alcoholism of some individuals." As yet scientists have been unable to fully trace a chain of events leading from genes to behavior, however, scientists have recently begun to identify specific genes that influence cognitive abilities and disabilities, most of which involve rare single-gene disorders such as phenylketonuria (PKU), Fragile X mental retardation and the early-onset familial form of Alzheimer's 5 disease (Plomin & Petrill, 1997; Steen, 1996).Just how important are genes? The "Central Dogma" of molecular biology, attributed to Francis Crick, is that "DNA makes RNA, RNA makes protein, and proteins (to oversimplify just a bit) are us' (Kaye, 1992)." If this true, then DNA is simply a "blueprint" that determines our humanity, but things are definitely more complicated. For example, we have evidence that mutations do not arise solely from genes, but may arise from cell structures as well: consider Sonneborn's melon-striped paramecia experiment (Goodwin, 1994). He was able to remove patches of cilia from the surface of a normal paramecium and put it back in reverse orientation, creating a "melon stripe." All future generations of this paramecium were melon striped with the same reversed row of cilia. Sonneborn demonstrated the same effect, cytoplasmic inheritance, on an asexually reproducing worm (Stenostomum). In sexual reproduction, one cell from the female and one from the male unite to produce the cell for the new organism. The male contribution consists solely of chromosomes, wh...
