Featuring information on Anne McCaffrey's Pern, including Dragonhealing, Herbalry, and Dracogenetics. |
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This text is compiled from factual, statistical, or other information originally from work done and/or owned by Anne McCaffrey. Credit is also given to Dr. Jack Cohen, who developed the theoretical basis for the McCaffrey-Cohen model. Statements expressed herein are ideas that may or may not coincide with those of Anne McCaffrey or Dr. Jack Cohen, and those ideas that have no readily available backing by either of the aforementioned are in no way to be interpreted as direct statements of the views, opinions, and/or statments made by the aforementioned.
White dragons are a special case scenario and are often rare, but the laws of genetics dictate that they are not an abnormality, they merely are naturally selected against. The genetic altering by Kit Ping Yung probably first introduced the possibility of a "white" dragon, because its genetic ancestor, the fire-lizard, has no genes for white offspring. The genes for white dragons are sex linked with the dominant gene completely dominant to the recessive gene. There are two genes, W or w and D or d. We can discard the idea that the mutation appeared naturally, as the condition is generally fatal and always produces a sterile offspring. If it had occurred as a mutation, it would not be present in the population at all. These genes were probably originally a developmental adjustment inserted by Kit Ping Yung. Because they are sex-linked, they trigger gender-specific alterations designed to produce defective fire-stomachs in queen dragons and an inherent sterility in green dragons given ingested firestone. Also, because these genes are sex-linked, there are two of them, one backing up the other, each doing the same thing, so that no matter which chromosome is passed to the offspring, if the offspring is female, then there will be at least one W or one D to act. The recessives were installed as self-destruct countermeasures, to prevent any deviant offspring from emerging. The mechanism effectively produced an offspring in a shell too thick to be emerged from normally, thus aborting the dragon. The Xg is used in conjunction with the W and d, and the XG with the w and D. When they were coded into the draconic genome, they were installed in a position to minimize crossover frequency. However, minimizing the crossover frequency does not completely eliminate it. Crossover will occur during meiosis, and thus the queen dragon can produce gametes with WD and wd combinations. At this point, one of two things can happen. First, the X chromosome on which the wd combination lies may be coupled with a Y chromosome, and the wd genes express themselves, producing a male. Second (although this is even rarer), the X chromosome with the wd combination can pair with another X chromosome with a wd combination. Thus white dragons may be female, though probability favors the male. Given a combination like this, the self-destruct kicks in, and produces the thick shell. However, the component coded for by the wd gene combination not only engages the self-destruct, but also severely limits the expression of rank and color genes to the point where the basest layer of white is revealed. (White, as a color, is when the hide will reflect all wave lengths of light. Variances in the hide may result in single colors being reflected, which is the effect Jaxom described as Ruth being all dragon colors, not an absence of any.) Attributes of this gene also include increased intelligence, long-term memory, and a substantially decreased adult size. However, if the hatchling is viable and given assistance, it will be healthy. Note that Anne has said there will be no more white dragons in general. Although this site espouses the belief that white dragons are possible, but rare, Anne is the last word. In case you didn't catch that: no white dragons. They're cool and unique, but not for us mere interlopers.
NOTE: These pages were developed from an earlier work by an unknown author. If you are this author or you know who the author is, please email me at [email protected] and I will credit it correctly. All references to worlds and characters based on Anne McCaffrey's fiction are copyright© Anne McCaffrey 1967,2000, all rights reserved, and used by permission of the author. The Dragonriders of Pern® is registered U.S. Patent and Trademark Office, by Anne McCaffrey, used here with permission. Use or reproduction without a license is strictly prohibited.
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