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Posted by chrish on April 17, 2003 at 08:13:36:
In Reply to: genetics posted by NAHerps on April 09, 2003 at 20:06:27:
bye the way, Brian Macker, recessive traits are often less common in the wild because they only are exhibited if the creature carries two recessives, while it will show a dominant trait with just one dominant
While that is true that recessive phenotypes only appear in homozygotes, it is not necessarily true that the recessive phenotype is less common than the dominant phenotype. In many cases, the recessive phenotype can be more common, particularly in a localized area. This is a question of population genetics and allele frequencies, not Mendelian genetics. Just because it is recessive doesn't mean it has to be rare. What if a recessive phenotype gives a selective advantange, for example?
therefore, there are less redheads and blondes in the world not because they are slaughtered at an early age, but because they are recessive traits.
There are less redheads and blondes in the world because over one half of the earth's population lives in the nations of China, India, Indonesia, Pakistan, Bangladesh, Nigeria, and Japan. The alleles that produce red hair and blonde hair are almost non-existant in those countries.
And red hair is complicated by the fact that it is one of the few human traits that shows negative assortment, meaning that redheads appear to avoid each other when it comes to marriage/mating. They don't marry each other as frequently as they should based on their population density. (For most other traits, humans assort positively - i.e. they marry/mate with people who look like they do).