mayoraasei | (no subject)

I'm slightly annoyed with one guy on the GSeed forums I go to, but I'm more annoyed with my insufficient grasp of knowledge on this matter.

Random person: Even if the person looks right and show desired phenotypes, their genetic sequence may be all messed up. Give that a few generations and things will stop working.
This guy: Actually, by reproducing with individuals who have a lot of gentic differences, it'll be eventually corrected..
Random person: Um...no...it does not eventually correct itself. Also phenotypes are generally multifactorial that means that more than one gene is responsible. Sometimes when you want something, it will stuff up the other parts.
This guy: There's always more than one responsible, which is why i usally say "gene sequence" as opposed to just "gene". And yes, they will correct themselves, because that's the whole point of genetic variation. That sequences that are faulty have a higher chance of not being expressed, whereas other that appear to function much better will be, and most-likely rendered dominant.
([sic] to all typos and grammatical mistakes above)

Okay, for people who do bio here, or any sort of science-related stuff and damn it I know you exist except you never read your LJ! Or reply to me! Anyway, is this guy correct? Does his claims have scientific basis? Are there scientific evidence to show that faulty sequences are less likely to be expressed?

Besides, dominance of a fitter gene isn't the end-all for evolution. Even if faulty genes are recessive, they are still expressed though only to a lesser extent. It does not eliminate the fact that faulty proteins will still be made. Put that alongside with "incomplete penetrance" (jargon) of a dominant gene, the matter becomes a lot more complicated than a simple dominance of fitter gene over the recessive faulty gene. Recessive genes are still inherited and passed down, more dangerous to a population in the long run because they are recessive. Because they can be masked by dominant genes, they are not lethal unless the child is homologous (=have both recessives). That means the gene can survive for much longer than a dominant lethal gene because it doesn't kill everyone that has the gene. I.e. faulty genes do not correct themselves!!

Also, it has been shown that although homologous recessive faulty genes can cause severe disease, those heterozygous (ie. have both the "normal" gene and the faulty gene) for the trait can actually benefit. The classic example is sickle cell anaemia: those that have both recessives get the anaemia, but those that have one dominant normal and one recessive is defended against malaria - making their survival a lot better in tropical zones than those who have both dominant normal genes. (They think it might also be the case with cystic fibrosis, but it hasn't been confirmed yet). Basically, some of the genes that cause diseases might actually in some other way be more helpful to the survival. So, there would be a problem if they correct themselves!

And lastly, what does "reproducing with individuals who have a lot of gentic differences" mean? How can one individual have more genetic difference than another individual? ==;

Anyway, most of the people who read this probably had the entire thing fly over their heads. Sorry ^^;;