dr. sinister

Actually the outbreeding population would not have gene frequencies of, 25% 50% 25% Because, the heterozygotes will always mate with a homozygote, heterozygotes will only exist in that one family with the recessive gene. And breeders use inbreeding to express homozygous traits, but not to flush out unwanted traits quicker.

Well, I'm talking about the outbreeding population. The inbreeding population would be different.

Well that's true the recessive allele can become hidden. But in an non-inbreeding population you get a system of heterozygotes breeding with homozygotes since all the population outside of the family are assumed to be homozygotes. So you would see a similar but quicker result with the outbred population.

Right but outbreeding has selection as well and it's more realistic than the selection with he inbred population, since people will always choose to mate with someone outside the family the recessive gene will disperse at a certain frequency through out the population. However, since every individual will choose a mate outside of the family the chance of the recessive allele spreading to successive generations becomes smaller and smaller and eventually by way of probability disappear from the population. So the selection in outbreeding is that each individual finds a mate that is unrelated to them genetically. In that case wouldn't you assume the outbred population to remove the trait faster? Or to a negligible frequency in far less time than an inbred population?

But I don't think inbreeding with even just one locus results in a faster flushing out of the trait. Because by the 3rd generation 37.5% (as Sisyphus has calculated) of the heterozygous recessive trait still exists in the inbred population. While by the 3rd generation in an outbreeding population there is only a 6% (as I've calculated it, I may be incorrect) frequency of the heterozygous trait. Provided that every generation breeds outside of the family. So by that logic, the trait would not be flushed out faster, even when dealing with one locus.

Thanks, Sisyphus. That was helpful, I'm not sure if it's entirely correct though, it very well may be. I think it maybe the formatting that's misleading, maybe some annotation would clarify your procedure. And Mokele, My purposes are to simply demonstrate the effects of inbreeding in a certain population. Even though human genetic disorders aren't quite so simplistic, I just wanted a way of easily showing the population frequencies as a result of multiple generations of inbreeding. I was having a discussion with someone and they made the claim that inbreeding flushes the autosomal recessive disorder out of the gene pool quicker than outbreeding and I'm pretty confident that this isn't the case. Outbreeding results in as I calculated it a 6% frequency of the Nr genotype by the 3rd generation and entirely eliminates the possibility of the homozygous recessive genotype by the 1st generation. But I wasn't entirely sure about calculating the frequencies of the inbred population. But I think the rule of thumb is a tendency towards homozygous genotypes with population inbreeding. Does anyone have any thoughts on this?

Hmm, I got a different result, but I think the error is mine. In calculating the mating possibilities of generation 2, I assumed that there were only 3 possible combinations. Can you provide the working so I can take a look at it?

Here's a hypothetical genetics problem, we assume that simple Mendelian principles apply. There is a population that carries a recessive genetic disorder ‘r’, which is expressed only when an individual inherits two recessive traits, or 'rr'. If there is a starting population of two recessive carriers... "Nr" and "Nr". If they were to mate, show the resultant population frequency for the 1st, 2nd and 3rd generations, assuming that the individuals with the expressed form of the recessive disorder do not survive to reproduce. I.e. in each generation what will be the percentage of those who have "NN", "Nr", "rr". P.s. Don't be a stickler about the wording I kinda just winged it when I wrote up the question. I've worked it out myself, I just want to know if others will get the same result. Thanks.