Monday, April 23, 2007

Haldane's Dilemna

Recently a post at Uncommon Descent detailed Walter ReMine's difficulties in obtaining alleged evidence in favor of a solution for Haldane's Dilemna. In a prior post I had written:

"Is a recessive mutation, causing a deleterious phenotype, selected against? Of course if the mutation is not expressed because of a dominant allele there is no basis for selection. But if there are two recessive alleles and a deleterious trait is expressed, will the reproductive fitness of the effected organism be compromised? Probably not."

The analysis of Haldane's Dilemna has not kept pace with developments in molecular biology. There have been some admirable attempts to precisely define the problem and there have been efforts directed at a solution. A formula intended to address both is the following:

P = 1-e^-4Nsq/1-e^-4Ns

where:

N = the population size
e = the natural logarithms base
P = the fixation probability
The fitness of different genotypes is represented 1, 1+s, 1+2s... s being positive when advantagous and negative when deleterious.
q = initial frequency

The problem with the foregoing lies with an inability to assess all relevant variables within a genome. Genes can be identified in isolation for the purpose of assessing their impact- be it advantagous or deleterious. However we are unlikely to know with precision both the number of genes contributing to the genetic load and their collective impact on reproductive fitness for both an organism and the relevant population.

I'm not, of course, the only one who has observed an intrinsic uncertainty to analyses of Haldane's Dilemna. But this only affords further credence to suspicions about the credibility of computer programmed solutions; particularly those whose code is unavailable.

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