Masatoshi Nei

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Persistence of Common Alleles in Two Related Populations or Species

Genetics, 1977

Mathematical studies are conducted on three problems that arise in molecular population genetics.... more Mathematical studies are conducted on three problems that arise in molecular population genetics. (1) The time required for a particular allele to become extinct in a population under the effects of mutation, selection, and random genetic drift is studied. In the absence of selection, the mean extinction time of an allele with an initial frequency close to 1 is of the order of the reciprocal of the mutation rate when 4Nv << 1, where N is the effective population size and v is the mutation rate per generation. Advantageous mutations reduce the extinction time considerably, whereas deleterious mutations increase it tremendously even if the effect on fitness is very slight. (2) Mathematical formulae are derived for the distribution and the moments of extinction time of a particular allele from one or both of two related populations or species under the assumption of no selection. When 4Nv << 1, the mean extinction time is about half that for a single population, if the two ...

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The Molecular Approach to Evolution: Molecular Evolutionary Genetics

Science, 1987

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Variation and Covariation of Gene Frequencies in Subdivided Populations

Evolution, 1965

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M., 1987 Molecular Evolutionary Genetics

Bulmer, MG, 187

Evolutionary dynamics of genetic diversity

Ecological Modelling, 1986

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Theoretical Population

Genome Diversity and Evolution: AGA Symposium Issue

Section EVOLUTIONARY GENOMICS: Co-editor

Introductory remarks to the review series on gene therapy

Trends in Genetics, 1994

Theoretical Population Biology

B Gillespie, JH, 35 M

Concerted and Nonconcerted Evolution of the Hsp70 Gene Superfamily in Two Sibling Species of Nematodes

Mol Biol Evol, 2003

We have identified the Hsp70 gene superfamily of the nematode Caenorhabditis briggsae and investi... more We have identified the Hsp70 gene superfamily of the nematode Caenorhabditis briggsae and investigated the evolution of these genes in comparison with Hsp70 genes from C. elegans, Drosophila, and yeast. The Hsp70 genes are classified into three monophyletic groups according to their subcellular localization, namely, cytoplasm (CYT), endoplasmic reticulum (ER), and mitochondria (MT). The Hsp110 genes can be classified into the polyphyletic CYT group and the monophyletic ER group. The different Hsp70 and Hsp110 groups appeared to evolve following the model of divergent evolution. This model can also explain the evolution of the ER and MT genes. On the other hand, the CYT genes are divided into heat-inducible and constitutively expressed genes. The constitutively expressed genes have evolved more or less following the birth-and-death process, and the rates of gene birth and gene death are different between the two nematode species. By contrast, some heat-inducible genes show an intraspecies phylogenetic clustering. This suggests that they are subject to sequence homogenization resulting from gene conversion-like events. In addition, the heatinducible genes show high levels of sequence conservation in both intra-species and inter-species comparisons, and in most cases, amino acid sequence similarity is higher than nucleotide sequence similarity. This indicates that purifying selection also plays an important role in maintaining high sequence similarity among paralogous Hsp70 genes. Therefore, we suggest that the CYT heat-inducible genes have been subjected to a combination of purifying selection, birth-anddeath process, and gene conversion-like events.

format_quoteTwenty-two Hsp70 genes identified in C. briggsae; ten are full-length, compared with ten Hsp70s in C. elegans.format_quote

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Major Gene Families in Humans and their Evolutionary History

Human Population Genetics I Evolution and Variation, Oct 1, 2007

Drift variances of FST and GST statistics obtained from a finite number of isolated populations

Theoretical Population Biology, Jul 1, 1977

Abstract Approximate formulas for the mean and variance of the F ST or G ST statistic in a finite... more

Modification of linkage intensity by natural selection

Genetics, Nov 14, 1967

ENETIC linkage or linkage of genes is one of the common genetic features G of all organisms from ... more ENETIC linkage or linkage of genes is one of the common genetic features G of all organisms from viruses to man. It may be of great concern to evolutionary geneticists how genetic linkage was developed and how the intensity of linkage has been adjusted in the evolutionary process. FISHER (1930) suggested that "the presence of pail-s of factors in the same chromosome, the selective advantage of each of which reverses that of the other, will always tend to diminish recombination, and therefore, to increase the intensity of linkage in the chromosomes of that species." He also recognized another agency which would increase recombination, namely, ithe constant spread of advantageous mutations which, unless they occur so seldom that each has become predominant before the next appears, can only come together in the same gamete by means of recombination. This problem was recently discussed at length but still semi-quantitatively by BODMER and PARSONS There is a large amount of evidence that linkage intensity is under genetic control (cf. . In Drosophila ananassue, for example, MORIWAKI (1940) identified a dominant gene, En-2, located on the right arm of the second chromosome, which enhances recombination between almost every pair of loci on the same chromosome in both males and females, while KIKKAWA (1937) found another gene (or genes) which induces crossing over in males in the third chromosome. and also reported several recombination-deficient mutants in Escherichia coli K-12, which are probably due to single-gene mutation. Further, the effectiveness of artificial selection in reducing or increasing recombination values was reported by DETELFSEN and ROBERTS (1921), PARSONS in Drosophila.

format_quoteThe frequency of a recombination-reducing gene generally increases when loci show epistasis, affecting evolutionary trajectories.format_quote

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Natural Selection at the Class II Major Histocompatibility Complex Loci of Mammals: Discussion

Philosophical Transactions of the Royal Society B Biological Sciences, 1994

The role of natural selection at major histocompatibility complex (MHC) loci was studied by analy... more The role of natural selection at major histocompatibility complex (MHC) loci was studied by analysis of molecular sequence data from mammalian class II MHC loci. As found previously for the class I MHC molecule and a hypothetical model of the class II molecule, the rate of non-synonymous nucleotide substitution exceeded that of synonymous substitution in the codons encoding the antigen recognition site of polymorphic class II molecules. This pattern is evidence that the polymorphism at these loci is maintained by a form of balancing selection, such as overdominant selection. By contrast, in the case of monomorphic class II loci, no such enhancement of the rate of non-synonymous substitution was observed. Phylogenetic analysis indicates that, in contrast to monomorphic (&amp;amp;#39;non-classical&amp;amp;#39;) class I MHC loci, some monomorphic class II loci of mammals are quite ancient. The DMA and DMB loci, for example, diverged before all other known mammalian class II loci, possibly before the divergence of tetrapods from bony fishes. Analysis of the patterns of sharing of polymorphic residues at class II MHC loci by mammals of different species revealed that extensive convergent evolution has occurred at these loci; but no support was found for the hypothesis that MHC polymorphisms have been maintained since before the divergence of orders of eutherian mammals.

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