These two-locus genotype frequencies can be used to derive the frequencies of the maternal M -locus—offspring O -locus combinations to which we assign fitness. These maternal—offspring genotype frequencies are denoted F ij , with subscripts following w ij given in the Description of the Model section above and are presented in Table 2.
These frequencies are not two-locus genotype frequencies, but rather, are frequencies at which the various O locus genotypes in offspring are associated with the various M locus genotypes in their mothers. Empty cells have zero frequencies under Mendelian inheritance. We thank Ed Harris, Per Smiseth, Paula Kover, Allen Moore, and three anonymous referees for insightful comments on a previous draft of this manuscript.
Abstract Imprinted genes are expressed either from the maternally or paternally inherited copy only, and they play a key role in regulating complex biological processes, including offspring development and mother—offspring interactions. Description of the Model Single-locus model. Two-locus model. Population mean fitness, calculated as above, is now determined by the fitness values and frequencies of the maternal M -locus—offspring O -locus combinations, and is given by For both models, we used the genetic covariance between the maternal and offspring traits [cov m , o ] to quantify the adaptive genetic integration of traits expressed in mothers and their offspring [ 24 ].
Results The key question of whether the assumed model of selection favors the evolution of genomic imprinting can be examined by analyzing the effect of the level of imprinting on population mean fitness.
The Neutral Theory
In the single-locus model, partial differentiation of population mean fitness Equation 1 with respect to the level of imprinting yields a simple expression for the effect of imprinting on population mean fitness This equation demonstrates that imprinting is favored by selection whenever there is genetic variation at a locus affecting the maternal and offspring traits involved in the maternal—offspring interaction.
For the two-locus model, the effect of imprinting on population mean fitness is again given by the partial derivative of population mean fitness with respect to the level of imprinting, which yields This expression shows that imprinting is favored whenever there is linkage disequilibrium between the pair of loci affecting the maternal and offspring traits. In both models, imprinting has the same effect on maternal—offspring coadaptation: in the single-locus model, imprinting has the potential to double the genetic covariance between maternal and offspring traits, and in the two-locus model, imprinting doubles the contribution of linkage disequilibrium to the genetic covariance Thus, again, imprinting affects population mean fitness via its effects on the maternal—offspring genetic covariance.
Discussion The key result of our model is that natural selection favors the evolution of genomic imprinting, because it increases offspring fitness by enhancing the genetic integration of coadapted offspring and maternal traits. Materials and Methods Derivation of maternal—offspring genotype frequencies for the single-locus model. Download: PPT. Derivation of maternal—offspring genotype frequencies for the two-locus model. Supporting Information. Table S1.
JW derived the model. JBW and RH wrote the paper.
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Synonymous mutations break their silence | Nature Reviews Genetics
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J Cell Physiol — Gavrilets S One-locus two-allele models with maternal parental selection. Wade MJ The evolutionary genetics of maternal effects. Maternal effects as adaptations. Oxford: Oxford University Press. Hager R, Johnstone RA Differential growth of own and alien young in mixed litters of mice: A role for genomic imprinting.
Ethology — Hager R, Johnstone RA The influence of phenotypic and genetic effects on maternal provisioning and offspring weight gain in mice. Remarkably, his description of silent genes was found to correspond precisely with the so-called junk genes. Just as Collins predicted, the vast majority of significant mutation in the genomes of complex species arises from the silent genes. But Collins' powerful and ambitious theory moves well beyond the molecular realm.
He argues that while natural selection is a major force in evolution, the great driver of complex evolution is the range of variation created by the silent genes.
As Professor Donald Braben writes in his illuminating foreword, "Collins is proposing a general evolutionary theory which, if it continues to be supported by the data, may in due course come to rival Darwin's theory that evolution is driven by natural selection. This work proposes to resolve two central mysteries of evolutionary biology: why organisms' genomes are filled with large amounts of genetic coding sequences with no known function some He argues that the so-called "junk DNA" consists of silent genes that are not subject to the normal processes of natural selection and thus can evolve freely over long periods of time without adversely affecting the host organisms.
He further argues that a strong theory of variation as the driver of evolution provides a better general theory of evolution than Darwin's theory that evolution is driven by natural selection. Previously unavailable in the US. Charles Darwin wrote in The Origin of Species that "unless profitable variations do occur, natural selection can do nothing.
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Selfish traits not favoured by evolution, study shows
Any warranty descriptions were intended for US purchasers. Review This work proposes to resolve two central mysteries of evolutionary biology: why organisms' genomes are filled with large amounts of genetic coding sequences with no known function some No customer reviews. Most helpful customer reviews on Amazon. In a situation of strict control and censorship of information such as during the Franco dictatorship, it may be more difficult to infer the climate of opinion from the newspapers. Nevertheless, the intrinsic tension seen in the press, as businesses involved in providing information, shows an interesting compromise between what the public wanted and what was allowed by the censors.
This special context adds even more interest, if that were possible, to one of the questions James Secord raises in his "Knowledge in Transit": "How and why does knowledge circulate? In approaching this case, it is indispensable to take into account the appropriation processes that involved evolution when it first arrived in Spain, as some of them shaped those that took place during the Franco regime. The reception of Darwinism in 19th century Spain is a well-studied case Historians have shown that it was not simply pure dissemination of scientific knowledge, but an appropriation in which the context of Spain at that time, a moment of revolution, played a central role Some sectors of society adopted evolutionary theory and used it as both a symbol for their own ideals and as an instrument to back a host of often very different arguments.
It was associated with progressivism, liberal thinking, revolution, socialism, communism, etc. Conservatives therefore disapproved of it In the 20th century, before and during the Civil War, many supporters of evolutionary theory joined the Republicans After winning the war against the Spanish Second Republic, Franco used censorship and depurative policies to wipe out any trace of Republicanism that, by association, also affected the theory of evolution In addition, from , Franco strengthened his ties with the Catholic Church in order to avert political pressure from Europe.
Following the fall of his fascist allies at the end of World War II, he needed the Church's support to change the image of his policies by enhancing the Catholic elements and hiding those of a fascist nature, especially to the outside world. Catholic collaborationists offered him the powerful Catholic press network to defend the regime's cause abroad, but in return they demanded a more Catholic policy from the regime In practice this meant that political posts such as those in charge of censorship and education fell into Catholic hands Thus, control of the information reaching the public domain had to strictly follow Catholic dogma, which, although not officially, implicitly condemned evolution as a heresy Thus, in the climate of the Franco dictatorship, evolution would be at least a double heresy How far does this case reflect what could be found regarding evolution in the public domain?
In this section, I will defend that this newspaper can be taken as a good survey case model for such a study It must be borne in mind that the dictatorship controlled all the media, particularly the press, by reading all pre-prints before they reached the public. Thus, a certain uniformity was characteristic of the press, especially in early Francoism. La Vanguardia is one of the oldest newspapers in Spain. It was founded in and has been published without interruption ever since, except during the Civil War.
This demonstrates a considerable ability to adapt to political and social changes. This was a clear statement of intent: the journal was going to follow the new regime and support Franco's Nationalist policies In , with a new press act and a new director, a period of openness began at the newspaper and a change in vocabulary, style, structure and subject matter can be detected. At first the vocabulary was grandiloquent, praising Spain and Franco, with a very rigid pattern and a paucity of subjects.