{\displaystyle h} and 0 . μ Mutation–selection balance is an equilibrium in the number of deleterious alleles in a population that occurs when the rate at which deleterious alleles are created by mutation equals the rate at which deleterious alleles are eliminated by selection. / p {\displaystyle p} / s μ μ However, new deleterious alleles arise by mutation. h s {\displaystyle q=\mu /s} to decrease at rate {\displaystyle p_{AA}} {\displaystyle p=p_{AA}+p_{AB}} p . q Supposing there is selection against a deleterious allele. {\displaystyle s} {\displaystyle \mu } Equilibrium in the number of deleterious alleles in a population when creation equals elimination by negative selection. / respectively, where . p In the case of complete dominance ( to explain the persistence of deleterious alleles as in the case of spinal muscular atrophy,[5][4] or, in theoretical models, mutation-selection balance can appear in a variety of ways and has even been applied to beneficial mutations (i.e. {\displaystyle spq} {\displaystyle 2p_{AB}} {\displaystyle 1/(1-sp_{BB})} Learn how and when to remove this template message, "De Novo Rearrangements Found in 2% of Index Patients with Spinal Muscular Atrophy: Mutational Mechanisms, Parental Origin, Mutation Rate, and Implications for Genetic Counseling", "Beneficial Mutation–Selection Balance and the Effect of Linkage on Positive Selection", https://en.wikipedia.org/w/index.php?title=Mutation–selection_balance&oldid=976844169, Short description is different from Wikidata, Wikipedia articles that are too technical from September 2010, Creative Commons Attribution-ShareAlike License, This page was last edited on 5 September 2020, at 11:13. {\displaystyle h} {\displaystyle p_{BB}} is a number between , 1 {\displaystyle h=0} 1 = − Putting these two pieces together, we can write the expression for the change in allele frequency that is due to BOTH gene flow and selection: Dq = -m(qx t- qy t) - sqx2(1-qx). [1] This equilibrium frequency is potentially substantially larger than for the case of partial dominance, because a large number of mutant alleles are carried in heterozygotes and are shielded from selection. Mutation–selection balance then gives s , and so the frequency of deleterious alleles is h p Suppose that deleterious mutations from A to B occur at rate {\displaystyle q\approx \mu /hs} h p 1 {\displaystyle \mu } p μ because the mutation rate is so low that + Evolutionary Analysis, 5th Edition. = (ignoring back mutations). indicates that A is completely dominant while of normal alleles A increases at rate μ {\displaystyle h=0} ( . A s This case is approximately equivalent to the preceding haploid case, where mutation converts normal homozygotes to heterozygotes at rate {\displaystyle q} p {\displaystyle \mu }