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At least 55 records · Page 3Linked to original sources
PubMed1991

Coevolution of self-fertilization and inbreeding depression. III. Homozygous lethal mutations at multiple loci.

We study the evolution of the rate of self-fertilization in response to deleterious mutations at multiple loci. Although partial selfing induces associations among loci even in the absence of linkage, associations among mutations at different loci are of a smaller order of magnitude than the mutation rate. Genotypes that carry homozygous lethal mutations in heterozygous form at i loci occur in frequencies of the order (Ti) mu i, in which T denotes the number of viability loci and mu the mutation rate. While associations between mutations at different loci remain small even under inbreeding, each viability locus develops an association with the modifier of the rate of self-fertilization that substantially affects the evolution of the breeding system. Positive associations between enhancers of selfing and haplotypes carrying multiple wild-type alleles and positive associations in heterozygosity between the modifier locus and the viability loci promote evolutionary increases in the rate of self-fertilization.

Biometry↗
PubMed1992

Coevolution of cytokine receptor families in the immune and nervous systems.

Close relationships between the nervous system and immune systems at molecular levels have now become evident. Receptors for CDF/LIF and CNTF, i.e., factors which play important roles in the nervous system, share a close structural similarity to those for IL-6, which is a molecule acting in the immune system. Receptors for these three factors belong to a subtype of cytokine receptor family (class IB cytokine receptor). We have constructed a higher subdomain structure of the receptor for CDF/LIF based on its known primary structures. The receptor contains immunoglobulin and fibronectin-like domains, in addition to common domains of the cytokine receptor, similar to those cell surface molecules of the neural immunoglobulin gene super family. These domains appear to have similar structures to the immunoglobulin. These lines of evidence suggest that the class IB cytokine receptor was formed as a result of those fusion of the genes for a more primitive cytokine receptor IA and for the neural immunoglobulin super gene family, and that, likewise, many molecules regulating neural development and those which act in the immune system have a common evolutionary origin.

Amino Acid Sequence↗
PubMed1988

Gene-culture coevolution: a test of the steady-state hypothesis for gene-culture translation.

Although there has been considerable discussion of the gene-culture theory (GCT) approach to biocultural systems, relatively little critical attention has focused on the specific approximations used in GCT, or on their improvement. Here we consider the steady-state hypothesis used in GCT models to connect activity on the level of individual choice behavior to the level of societies taken as wholes. The hypothesis is tested by using Monte Carlo techniques to estimate solutions to the dynamical equation for social order. The steady-state hypothesis is found generally to be invalid for all the categories of choice function originally considered by Lumsden and Wilson, but acceptable for the highly restricted parameter ranges used in their treatments of the gene-frequency change. The implications for the development of improved gene-culture modeling techniques are discussed.

Computer Simulation↗
PubMed1988

Phylogenetic trees support the coevolution of parasites and their hosts.

The close correspondence often observed between the taxonomy of parasites and their hosts has led to Fahrenholz's rule, which postulates that parasites and their hosts speciate in synchrony. This leads to the prediction that phylogenetic trees of parasites and their hosts should be topologically identical. We report here a test of this prediction which involves the construction of phylogenetic trees for rodents and their ectoparasites using protein electrophoretic data. We find a high degree of concordance in the branching patterns of the trees which suggests that there is a history of cospeciation in this host-parasite assemblage. In several cases where the branching patterns were identical in the host and parasite phylogenies, the branch lengths were also very similar which, given the assumptions of molecular clock theory, strongly suggests that the speciation of these hosts and ectoparasites was roughly contemporaneous and causally related.

Animals↗
PubMed1985

Gene-culture coevolution: models for the evolution of altruism with cultural transmission.

Models of sexual haploids under kin selection are constructed. The trait of altruism is transmitted vertically from parent to child, but not in a strictly genetic manner. Two systems of altruism are considered: parent-to-offspring and sib-to-sib. In the former case it is shown that even when Hamilton's conditions for the success of genetically determined altruism are met, genes that increase the transmission of altruism may not invade the population. With sib-to-sib altruism, such genes will always increase initially.

Alleles↗
PubMed1986

Gene-culture coevolution of complex social behavior: human altruism and mate choice.

The hypothesis is examined that genes bias the development of complex social behavior in one direction over alternatives. Studies of altruism and political attitudes in twins estimate that approximately 50% of the variance is associated with direct genetic inheritance, virtually 0% with the twin's common family environment, and the remainder with each twin's specific environment. Studies of human marriages show that spouses choose each other on the basis of similarity, assorting on the most genetically influenced of a set of homogeneous attributes. These data imply a genetic canalization of social influences such that, within the constraints allowed by the total spectrum of cultural alternatives, people create environments maximally compatible with their genotypes.

Altruism↗
PubMed1987

cDNA sequence of a human skeletal muscle ADP/ATP translocator: lack of a leader peptide, divergence from a fibroblast translocator cDNA, and coevolution with mitochondrial DNA genes.

We have characterized a 1400-nucleotide cDNA for the human skeletal muscle ADP/ATP translocator. The deduced amino acid sequence is 94% homologous to the beef heart ADP/ATP translocator protein and contains only a single additional amino-terminal methionine. This implies that the human translocator lacks an amino-terminal targeting peptide, a conclusion substantiated by measuring the molecular weight of the protein synthesized in vitro. A 1400-nucleotide transcript encoding the skeletal muscle translocator was detected on blots of total RNA from human heart, kidney, skeletal muscle, and HeLa cells by hybridization with oligonucleotide probes homologous to the coding region and 3' noncoding region of the cDNA. However, the level of this mRNA varied substantially among tissues. Comparison of our skeletal muscle translocator sequence with that of a recently published human fibroblast translocator cognate revealed that the two proteins are 88% identical and diverged about 275 million years ago. Hence, tissues vary both in the level of expression of individual translocator genes and in differential expression of cognate translocator genes. Comparison of the base substitution rates of the ADP/ATP translocator and the oxidative phosphorylation genes encoded by mitochondrial DNA revealed that the mitochondrial DNA genes fix 10 times more synonymous substitutions and 12 times more replacement substitutions; yet, these nuclear and cytoplasmic respiration genes experience comparable evolutionary constraints. This suggests that the mitochondrial DNA genes are highly prone to deleterious mutations.

Base Sequence↗
PubMed1989

Coevolution of host and pathogen populations in the Hordeum vulgare-Rhynchosporium secalis pathosystem.

Isolates of Rhynchosporium secalis collected from two experimental barley populations were scored for putative isozyme, colony color, and virulence loci. Allelic frequencies, multilocus haplotype frequencies, and multilocus genetic structure differed in the two populations of R. secalis; haplotypes also differed widely from each other in virulence. The average virulence of isolates collected from the more resistant host population was greater than the average virulence of the isolates collected from the less resistant host population; also the least virulent haplotype, which made up 19% of the pathogen population collected from the less resistant host population, accounted for only 0.3% of the isolates collected from the more resistant host population. It was concluded that the genetic systems of the barley host and fungal pathogen interacted in a complementary fashion and that the genetic structures of both the host and pathogen populations were shaped by coevolutionary processes featuring interactions among loci affecting many different traits, including interactions among host resistance genes and pathogen virulence genes.

Biological Evolution↗
PubMed1992

Gene-culture coevolution: toward a general theory of vertical transmission.

A general formulation of cultural and genetic transmission is developed. The cultural transmission is vertical and the genetics may involve multiple loci. Each individual is represented by a phenogenotype, and conditions are given under which the evolutionary dynamics of phenogenotype frequencies are reducible to phenogametic or phenoallelic frequencies. The interaction between genes and culture is specified by an association measure, and results on the order of magnitude of this association at equilibrium are presented.

Biological Evolution↗
PubMed1989

Coevolution of the major histocompatibility complex and the t-complex in the mouse. I. Generation and maintenance of high complementarity associations.

A quantitative model is developed to explore the effects of prezygotic and postzygotic incompatibility on the origin and maintenance of associations between the major histocompatibility complex (MHC) and the t-complex in the mouse. Incompatibility is represented by a reduction in the rate of conception or gestation of offspring derived from sperm bearing MHC antigens in common with the mother. Incompatibility encourages the evolution of associations from a state of complete independence between the two complexes by promoting the invasion of all novel antigens, including those that exhibit associations with the t-complex. Incompatibility can modify the relative numbers of antigens associated with each haplotype by actively promoting the exclusion or invasion of recombinants that bear formerly +-specific or t-specific antigens on the alternative haplotype. The results of the analysis indicate that the state of complete independence between the MHC and the t-complex is not preserved over evolutionary time in the presence of incompatibility. Further, the expression of incompatibility maintains fully associated states that include a single antigen associated with the t-haplotype and up to three to five antigens associated with the +-haplotype within a single population.

Animals↗
PubMed1989

Coevolution of the major histocompatibility complex and the t-complex in the mouse. II. Modification of response to sharing of histocompatibility antigens.

Selective pressures imposed by high complementarity associations between the major histocompatibility complex (MHC) and the t-complex on a locus that modifies the expression of prezygotic and postzygotic incompatibility are investigated through the analysis of a quantitative model. Sharing of MHC antigens between mates or between mother and offspring elicits weak inhibition of conception or gestation. In the presence of high complementarity associations between the MHC and the t-complex, weak incompatibility depresses the mean fitness of the population. Nevertheless, natural selection favors the enhancement of the expression of incompatibility if the number of antigens associated with the +-haplotype exceeds the number associated with the t-haplotype by a sufficient margin. Under absolute linkage between the modifier locus and the t-complex, the number associated with the +-haplotype need only be greater than the number associated with the t-haplotype. In the absence of linkage, a twofold difference is sufficient to ensure the initial increase of modifier alleles that intensify the expression of incompatibility.

Alleles↗
PubMed1985

Coevolution of the glucose dehydrogenase gene and the ejaculatory duct in the genus Drosophila.

The glucose dehydrogenase gene (Gld) in Drosophila melanogaster exhibits a unique spatial and temporal pattern of expression. GLD expression switches from a non-sex-limited state at the pupal stage to a male-limited state at the adult stage. At the adult stage, the enzyme is restricted to the ejaculatory duct. Within the genus Drosophila, the ejaculatory duct has undergone a simple morphological divergence. In order to determine whether correlated changes in GLD expression had occurred, GLD activity during the pupal and adult stages was determined for several Drosophila species. It was found that virtually all of the species exhibit pupal GLD activity, whereas only those species with an expanded ejaculatory duct express male-limited GLD. The results of interspecific genital imaginal disc transplantation experiments indicate that the expanded morphology and GLD expression do not require any species- or sex-specific diffusible factors. An apparent regulatory polymorphism exists within the D. takahashii species with respect to male-limited GLD expression.

Animals↗
PubMed1992

Coevolution of the vertebrate integrin alpha- and beta-chain genes.

The integrin receptors are heterodimers whose alpha and beta subunits are encoded by separate, evolutionarily unrelated multigene families. Phylogenetic analysis of DNA sequences from these two gene families showed that they have not always evolved in a parallel fashion. The integrin alpha chains that can form heterodimers with beta 1 do not constitute a monophyletic group, nor do the beta chains which can form heterodimers with alpha V. On the other hand, the vertebrate alpha chains associating with beta 2 are a monophyletic group. In the metal cation-binding region of the alpha chain, an exon exchange took place between human alpha M and alpha X approximately 40-50 Mya, homogenizing this functionally important region in these two alpha chains. When integrin beta chains of different functional classes are compared, nonsynonymous (amino acid altering) nucleotide substitutions that alter amino acid residue charge in the central region of the molecule occur at a rate significantly higher than that expected under random replacement. By contrast, when closely related beta 1 chains are compared, residue charge is conserved in this region. These results pinpoint the central region as a focus of functional divergence among integrin beta chains, perhaps relating to the ability of each beta integrin class to associate with a specific array of alpha integrins. Furthermore, they imply that positive, directional selection on this region has occurred in the evolution of the integrin beta-chain gene family.

Animals↗
PubMed1989

Coevolution of virulent virus and resistant cells as a mechanism of persistence of herpes simplex virus type 1 in a human T lymphoblastoid cell line.

Infection of the lymphoblastoid CEM cell line with herpes simplex virus (HSV) type 1 results in a persistent infection with production of infectious virus. Evidence suggests that the persistent infection was not maintained by interferon or non-interferon-soluble antiviral inhibitors. Treatment of persistently infected cells with anti-HSV serum (termed CEMACR cells) or elevated temperature (39 degrees C) for 14 days (termed CEMTCR cells) resulted in loss of evidence of virus. HSV DNA was not detected in CEMACR or CEMTCR cells by Southern blot or in situ hybridization. The CEMACR or CEMTCR cells, however, were resistant to reinfection with homologous, parental virus (HSV0), but were susceptible to heterologous virus (vesicular stomatitis virus). Resistance to reinfection with HSV was not absolute; CEMACR or CEMTCR cells were less permissive to virus isolated from persistently infected cultures at times early in the course of infection, but were more permissive for HSV isolated at later times. Virus isolated later during persistent infection also displayed progressively increased virulence for the parental CEM cells. These results suggest that persistent infection of a human T lymphoblastoid cell line, CEM, with HSV-1 is maintained by a genetically determined cell-virus equilibrium, in which the resistance of cells and virulence of virus increase during persistence.

Animals↗
PubMed1977

Blood corpuscles and blood hemoglobins: a possible example of coevolution.

A model which equates oxygen transport to hemoglobin concentration and molecular weight is used to demonstrate that high concentrations of hemoglobin will augment oxygen transport only if the molecular weight of the hemoglobin is low. The evolution of corpuscles is a necessary counterpart to having high concentrations of the low molecular weight hemoglobins. corpuscles prevent loss of the small molecules by way of excretory filters and prevent the development of exceedingly high plasma osmotic pressures.

Biological Evolution↗