Genetic Diversity in a Collection

[sorraia]

i would say when species go extinct, thats negative. science doesnt tell us its negative, i say it is. science is neutral. its up to is to determine if its better when species go extinct, or if its better when species survive. climate change will cause mass extinction, and a conservation biologist should think thats bad.

Well good thing you aren't the authority!

I haven't given my opinion on the matter one way or the other, but I will say in general conservation biologists have the opinion of whether it is good or bad depending on the organism and where it happens. The extinction of the HIV virus would generally be considered a good thing to any one, no matter who you asked (Unless there was some sick individual who thought HIV infection was a good thing...). The local extinction of the Burmese python in Florida would be considered a good thing by conservation biologists, because Burmese pythons aren't native to Florida and are considered an invasive pest. Mass extinction across the globe is generally thought by the general populations to be a bad thing, but if you start asking individual scientists, you might get different answers. Extinction of one species is what allows other species to thrive. What matters more, in terms of ecology and conservation, is how quickly and how widespread the extinction is occurring, not whether it is occurring at all. Believe it or not, there ARE conservation biologists who believe all of our human efforts to preserve some species are meaningless if that species is unable to adapt to its changing world. Allowing that species to go extinct could mean another species is able to take over that niche, and new species may evolve as a result. In the natural world, these changes occur all the time. What conservation biologists are most concerned about is the affect human activity is having on the natural world, not those processes that naturally occur. Oh and by the way, scientists by and large can't even agree on whether the current climate change is man-made, natural, or natural influenced by human activity. But that's a whole different debate in and of itself.

science doesnt care if more or fewer sick and deformed snakes among the offspring is good or bad. but i say its better to have healthy hatchlings. and then science tells me that inbreeding is bad. when you think getting weakened snakes with a higher chance of genetic defects is perfectly alright, then inbreeding is perfectly alright.

Except science doesn't say inbreeding is bad. If healthier animals is better and inbreeding can actually produce healthier animals by eliminating deleterious traits, how can you say inbreeding is always bad? Inbreeding in and of itself doesn't cause illness and weakness, inbreeding simply concentrates those genes already in existence. If there is a deleterious gene in the population, that gene should be eliminated in order to produce stronger individuals. Constant outcrossing doesn't eliminate it, but actually keeps it in the populations by potentially spreading it throughout the population. Now you don't know which animals carry that gene and which ones don't, and it is only a matter of time before the right animals are paired and that trait comes out. By inbreeding, you can concentrate that gene within your population, identify which animals carry the gene, and eliminate them from your population. You then take the healthy surviving animals, continue to breed them to relatives (not necessarily close relatives), and again eliminate those animals carrying the gene. Continue until you have essentially eliminated that deleterious trait, and now you have a healthy line of linebred or inbred animals.

BTW, the homozygous form of sicke cell anemia is lethal, the heterozygous form has the advantage of making the individual resilient against malaria, but it has the disadvantage of shortened life expectancy, a higher chance of blood vessels getting blocked, and lower oxygen transport. but if you only have one copy, at least you are not dead, because you still have one healthy copy of the gene that makes red blood cells.

Having that sickle cell trait is better than being dead, but it is also not completely healthy, even though it makes the individual less susceptible to malaria. My point is, you are claiming heterozygosity is better than homozygosity, but in this case it is not.

and no matter how you want to put it, we generally have two healthy copies of each gene.

HOw do you know we generally have two "healthy" alleles (I'm assuming you mean allele when you say "copy") for each gene? Have you done genetic typing of all individuals? That is in fact false. There are a myriad of diseases, deformities, syndromes, defects, and weaknesses in the human population, due to the fact we DO carry so many deleterious genes. The same occurs in many captive bred animals who have not been specifically selected to eliminate those deleterious traits.

or you could say we generally have each gene two times in two locations, which is the same, at least according to 1 + 1 = 2. if you have two copies of a gene, one can be broken and the other one can be fine. and thats generally fine, well, not in the case of sickle cell anemia, that one sucks even in the heterozygous form. im not following the semantic contortions here. the key point is that it adds redundancy, it allows individuals to survive with one broken copy of a vital gene, because one broken copy leaves them with one copy that is intact. as in 2 - 1 = 1. if each gene is its own entity, it means i have two of each, because the genes sit on the chromosomes, and i have two of each of these. basically you are trying to tell me that 2 = 1, and therefore 2 - 1 can be equal to zero. nope, not buying it.

Actually, no. Diploid organisms have 2 of each chromosome. In humans, that's 23 chromosome pairs, or 46 chromosomes total. Each chromosome has a single allele for a single gene. That means we have 2 alleles for each gene. We don't have 2 copies of the gene, we have 2 alleles for that gene. If we had 2 copies of the gene, that would mean we had 4 chromosomes with 4 alleles. There are no "broken" gene copies. The ONLY exception to this rule is the case of sex chromosomes, where female mammals have 2 X chromosomes and male mammals only have 1 X chromosome and 1 Y chromosome. In this case, one of the 2 X chromosomes in females is deactivated, called the "Barr body". That deactivation is random though, and if a deleterious traits is coded for on one of those two X chromosomes, it can still be expressed. (I presume there is a similar mechanism in other diploid organisms, though I have not specifically researched it.) There are no second copies of genes to take over in case one gene is "broken" as you call it.

I think the problem here is you don't understand basic genetics. There are no "broken" genes, we don't have 4 chromosomes and 2 of every gene. We have 2 chromosomes, each pair of chromosomes has an area for 1 of each gene containing 2 alleles for each gene. In total, that gives us 1 of every gene, and 2 alleles for every gene. The only exception to this rule are where mistakes happen and an organisms inherits the wrong number of chromosomes (in some cases that organisms doesn't survive).

Here's a website with the basics that might be helpful: http://history.nih.gov/exhibits/genetics/sect1a.htm