Chris Anderson
Dr. House of Chameleons
Is there something in the water or just happens that the veileds that were imported, had this trait and because there aren't a lot of veileds bred there, it is more prevalent in the gene pool? (I am assuming the gene pool is small since It doesn't seem like that many people keep chameleons there?)
Its hard to say.
The translucent gene was found in a few imported specimens and then selectively bred for in captivity. This is fairly easy to do because the trait is expressed in any animal that carries the gene so you could select an animal that has the mutation out of the hundreds of thousands of animals that don't.
In recessive genes such as hypermelanism, you would only be able to pick out an animal that are homozygous for it so all of a sudden, you probably aren't going to be able to select the one animal that does have it. A common mutation rate in eukaryotes is 10^-5 or 10^-6 per base pair per generation. That basically means that one animal in 10,000 to 100,000 will have a mutation at the allele in question but they won't show it.
If we want to assume that the homozygous expression of this trait that is seen appeared because two unreleated animals with it happened to breed together, we need to assume that two individuals, conveniently of opposite sex, got the correct mutation that causes hypermelanism (there are a number of potential mutations that could occur so thats a big assumption). That means you have 2 individuals in 20k to 200k animals that you then have to by chance select and breed together. Needless to say, this doesn't happen too often.
On the other hand, if we assume that the homozygous expression is the result of inbreeding, we need to assume that one individual got the correct mutation (again, 1 animal in 10k-100k). That animal would then need to survive and be bred to a normal animal and 50% of the resulting offspring will have that trait (but not express it). If two of those offspring that do have the trait were then bred together, 1/4 of their offspring would show the trait. Obviously this doesn't happen very often either.
Its really just a matter of chance and in this case, it happened to express itself in England.
Chris