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Biomedical subjects

M W Feldman

Publications and source records attributed to M W Feldman.

At least 109 records · Page 6Linked to original sources
PubMed1982

Theory and observation in cultural transmission.

Cultural phenomena may show considerable stability over time and space. Transmission mechanisms responsible for their maintenance are worthy of theoretical and empirical inquiry; they are complex and each possible pathway has different effects on evolutionary stability of traits, as can be shown theoretically. A survey designed to evaluate the importance of some components of cultural transmission on a variety of traits showed that religion and politics are mostly determined in the family, a mode of transmission which guarantees high evolutionary stability and maintenance of high variation between and within groups.

Attitude↗
PubMed1981

Linkage relationships among five enzyme-coding gene loci in the copepod Tigriopus californicus: a genetic confirmation of achiasmiatic meiosis.

Linkage relationships among five polymorphic enzyme-coding gene loci in the marine copepod Tigriopus californicus have been determined using electrophoretic analysis of progeny from laboratory matings. Phosphoglucose isomerase (PGI; EC 5.3.1.9) was found to be tightly linked to glutamate-pyruvate transaminase (GPT; EC 2.6..1.2), with only one recombinant observed in 364 progeny; glutamate-oxaloacetate transaminase (GOT; EC 2.6.1.1) is linked to the PGI-GPT pair, with a recombination fraction of approximately 0.20 in male double heterozygotes. Phosphoglucomutase (PGM; EC 2.7.5.1) and an esterase (EST; EC 3.1.1.1) are not linked to the PGI, GPT, GOT grouping, which has been designated linkage group I. Reciprocal crosses have revealed that no recombination occurs in female T. californicus; this observation confirms a previous report that meiosis in female Tigriopus is achiasmatic.

Alanine Transaminase↗
PubMed1981

The estimation of epistasis in components of fitness in experimental populations of Drosophila melanogaster I. A two-stage maximum likelihood model.

Laboratory populations of Drosophila melanogaster bearing the Curly and Plum marked second chromosome inversions were observed in selection experiments for ten discrete generations. Maximum likelihood estimates of the relative fitnesses of Curly, Plum, Curly-Plum, and wild phenotypes were obtained from selection trajectories. Using these estimates, measures of multiplicative and additive epistasis were calculated. These were partitioned into pre-sampling and post-sampling components, and both were found to be significant. In several cases the sign of the epistasis of the two components was reversed, and the direction of net epistasis depended on the particular inversion. The significance of partitioning epistasis into components is discussed in the light of two locus population genetic theory.

Animals↗
PubMed1981

The estimation of epistasis in components of fitness in experimental populations of drosophila melanogaster II. Assessment of meiotic drive, viability, fecundity and sexual selection.

An analysis of fitness components was performed on laboratory populations of Drosophila melanogaster bearing Curly and Plum marked second chromosome inversions with two genetic backgrounds. Selective differences between Curly, Plum, Curly-Plum, and wild phenotypes were partitioned into meiotic drive, viability, fecundity and mating success. Although no significant meiotic drive was detected, there were significant differences between genotypes in the other three components. Interlocus interactions in fertility and sexual selection components were measured, and statistics to quantify epistasis at these levels of fitness were devised. Significant fitness interactions between genes on the Curly and Plum inversions in viability, fecundity, and sexual selection were found. These results were qualitatively consistent with the maximum likelihood fitness estimates found previously. The expected allele frequency trajectories computed from the estimated components adequately fitted the observed selection trajectories.

Animals↗
PubMed1981

Disequilibrium between linked inversions: an alternative hypothesis.

Data are presented which demonstrate a difference in the rate of recombination between cis and trans inversion double heterozygotes in Drosophila melanogaster. The corresponding two-locus theoretical model in which the double heterozygotes have different rates of recombination and no selection operates is analysed. We show that stable linkage disequilibrium can be maintained in this neutral situation. These results bear on the general observation in wild populations of several insect species that linked inversions manifest linkage disequilibrium.

Animals↗
PubMed1981

Population genetic theory of kin selection: Multiple alleles at one locus.

Exact population genetic models of one-locus sib-to-sib kin selection with an arbitrary number of alleles are studied. First, a natural additive scaling is established for the genotypic value associated with probabilities of performance of altruism. Two classes of polymorphic equilibria are possible, one corresponding to the usual one-locus viability equilibria and the other reflecting the kin-selection assumptions of the model. At both, the covariance between additive genotypic value and genotypic fitness vanish. Further, the sign of this covariance determines the fate of rare alleles introduced near the first class of equilibria. In addition, the covariance explains the differences between Hamilton's rule, which results from Hardy-Weinberg assumptions, and exact initial increase conditions.

Journal Article↗
PubMed1981

Population structure of multilocus associations.

A method of analysis is presented whereby the structure of multilocus associations among and within several populations can be partitioned into its components. The components are measured by their contributions to the variance in the number of heterozygous loci in two randomly chosen gametes. The singlelocus components are the average and the variation among populations in gene diversity and the variance among populations in allele frequency. The two-locus components include the mean and variance of disequilibria, the covariance of allele frequencies over populations, and various interactions. When applied to allozyme data from populations of wild (Hordeum spontaneum) and cultivated barley (H. vulgare), the analysis highlighted the repetitive pattern of the multilocus associations in the composite crosses whereas it emphasized the regionally localized and geographically variable pattern present in the natural populations of the wild species. The analysis is flexible and applicable to multilocus gametic data from any set of populations, without regard to the number of alleles per locus or the reproductive method of the organism.

Journal Article↗
PubMed1980

Evolution of recombination in a constant environment.

The theory of evolution at a selectively neutral locus that controls the recombination between two major loci that are under selection is studied. If the major loci are at a stable equilibrium in linkage disequilibrium under selection and recombination, then a mutation at the modifier locus will increase in frequency when rare if and only if it decreases the recombination fraction. If the major loci are in disequilibrium at a balance between selection against deleterious alleles and mutation towards them, then two new phenomena are observed. First, a recombination increasing mutation will succeed if the disequilibrium is negative and the modifier is sufficiently tightly linked to the major loci. Second, depending on the strength of selection, even if the disequilibrium is negative, recombination reduction may occur for looser linkage between the major and modifier loci.

Journal Article↗
PubMed1979

Neurotransmitter release statistics: moment estimates for inhomogeneous Bernoulli trials.

Evoked release of quanta of neurotransmitter is generally treated as a set of homogeneous, stationary Bernoulli trials, hence governed by the binomial distribution. Relaxing the assumptions of uniformity and stationarity leads to a more realistic physiological model of transmitter release but also introduces systematic biases in the moment estimates of the binomial parameters. We derive probability generating functions for quantal release and expressions for the moment estimates of n and p for a generalized model that incorporates temporal variation and nonuniformity in individual release probabilities and in numbers of release sites.

Action Potentials↗
PubMed1979

Evolutionary effects of contagious and familial transmission.

Two models involving non-Mendelian transmission of a discrete valued trait through within- and across-generation contagion are proposed in an investigation of the joint evolution of phenotype and genotype. A single locus with two alleles determines susceptibility to contagion. The incorporation of within-generation contagious transmission extends the parameter ranges allowing phenotypic polymorphism and introduces a new phenotypic equilibrium configuration. The latter is characterized by a threshold in the initial value of the trait which determines whether the trait can increase. Phenotypic evolution is accelerated by within-generation contagion, but the rate of genetic evolution is retarded relative to that under uniparental transmission across generations. The second model studied allows the trait to be acquired, at genotype-dependent rates, even if the transmitting parent does not have the trait. Both the pattern of phenotypic transmission and the selection on the trait influence the course of evolution. Some important aspects of the structure of the one locus-two allele model are shown to be preserved with more alleles. At equilibrium, the leading eigenvalue of the transmission-selection matrix assumes the role of genotypic fitness.

Alleles↗