Polymorphism of the Y-chromosome diallelic loci in the ethnic populations of the Altai-Sayan region

Using the data on five biallellic Y-chromosome loci (DYS199, 92R7, SRY1532, RBF5 and DYS287) polymorphism, genetic structures of the five Turkic-speaking ethnic groups of the Altai-Sayan highland (Tuvinians, Sojots, Shorians, Khakassians, and Southern Altaians (Altai-Kizhi), were described. The gene pools of the populations examined were characterized by the presence of pronounced paleo-Caucasoid component (92R7-T-lineages). The frequency of this component increased westward, reaching more than 70% in Shorians and Southern Altaians. Haplotype TAT-C (RBF5 locus) was observed in all populations, except Shorians, with the frequencies varying from 5.4% in Altai-Kizhi to 18.8% in Khakassians. The Alu-insertion in the DYS287 locus was revealed only in the Altaian sample with the frequency of 3.3%. It was established that the Altai-Sayan populations studied split into two statistically significantly different groups. One of the groups was represented by Tuvinians, Sojots, and Khakassians, while another one was comprised of Shorians and Altaians.     

Haplotypes of two diallelic Y chromosome loci in the indigenous and migrant populations of Siberia

Two diallelic Y-chromosome markers, the Y Alu polymorphism (YAP) and the T-C transition (Tat), were analyzed in the indigenous (Tuvinian, Buryat, Northern Altaic, and Tatar) and migrant (Slavic) populations of Siberia. A high frequency of the allele C was revealed in several indigenous populations (25-55%) and in Russians (20.8%). The YAP+ allele occurred at a surprisingly high frequency (31.4%) and was completely linked with the C allele in Buryats. The YAP+ chromosome was also found in the Tuvinian population (1.5%). The two diallelic loci showed a marked linkage disequilibrium (D = 92.4%) in the total sample. The YAP-/T and YAP-/C haplotypes prevailed in both indigenous and migrant populations: their respective frequencies were 80.4 and 19.6% in the Slavic population and 71.8 and 19.9%, respectively, in the indigenous one. The YAP+/C (7.8%) and YAP+/T (0.5%) haplotypes were found only in the indigenous population. An appreciable heterogeneity in haplotype frequency distribution between regional subpopulations was revealed in Russians, Tuvinians, and Buryats. The origin and evolution of Y-chromosome lines in Northern Asia are considered.     

The number of equilibria in the diallelic Levene model with multiple demes

The Levene model is the simplest mathematical model to describe the evolution of gene frequencies in spatially subdivided populations. It provides insight into how locally varying selection promotes a population’s genetic diversity. Despite its simplicity, interesting problems have remained unsolved even in the diallelic case.In this paper we answer an open problem by establishing that for two alleles at one locus and J demes, up to 2J−1 polymorphic equilibria may coexist. We first present a proof for the case of stable monomorphisms and then show that the result also holds for protected alleles. These findings allow us to prove that any odd number (up to 2J−1) of equilibria is possible, before we extend the proof to even numbers. We conclude with some numerical results and show that for J>2, the proportion of parameter space affording this maximum is extremely small.     

An agent-based model for predicting the prevalence of Trypanosoma cruzi I and II in their host and vector populations

Trypanosoma cruzi is the causative agent of Chagas disease, an endemic human parasitosis in Latin America. This protozoan is transmitted to human and other mammals by blood-feeding bugs belonging to the Triatominae subfamily. There are two strains (T. cruzi I and T. cruzi II) presenting different biological and ecological characteristics. An original agent-based model (ABM) was designed for predicting the prevalence (i.e., proportion of infected individuals in the total population at a given time) of T. cruzi I and II during single and mixed infections. The ABM was calibrated from experimental data retrieved from literature. It was shown that inclusion of reservoir hosts as supplementary type of agent in the model was necessary for obtaining realistic simulation results of the prevalence of the two strains. This is totally in agreement with experimental and field observations on the importance of reservoirs in the parasite transmission cycle. Proposals were made for refining the model. More generally, the advantages and limitations of the ABM in parasitology modeling have been discussed.     

Application of absorbing Markov chains to sib mating populations with selection for a pair of independent diallelic loci

In this paper we consider a sib mating population with a pair of independent diallelic loci. The average, variance, and third order moment about the mean have been calculated for the distribution representing the number of generations needed to reach an absorbing state beginning in any one of the trnsient states. Four cases are analysed: the no selection one and those cases arising from the combination of favorable selective values for the homozygous and heterozygous genotypes for both genes. The different cases are considered separately and compared, but only some typical starting cases have been reported so as to save space. No selective differences were assumed between the two sexes. The formalism of absorbing Markov chains have been used for the calculations.     

Equilibria and dynamics of selection at a diallelic autosomal locus in the Nagylaki-Crow continuous model of a monoecious population

Let birth rates and death rates be constant, birth rates positive, fertilities additive, and each birth rate not larger than twice any other birth rate. Global convergence to equilibria is proved for the model in the title. There is at most one polymorphic equilibrium or there are a continuum of equilibria. The phase portraits are given. If there is a polymorphic equilibrium, then the largest negatively invariant set in the state space is a continuous curve connecting the two fixation equilibria. This curve coincides with the Hardy-Weinberg manifold exactly when the death rate is additive. Disregarding extinction, the polymorphic equilibria are the same for the continuous model as for the corresponding discrete model exactly when the death rate is additive.     

A model for the evolution of paralog families in genomes

We introduce and analyse a simple probabilistic model of genome evolution. It is based on three fundamental evolutionary events: gene loss, duplication and accumulated change. This is motivated by previous works which consisted in fitting the available genomic data into, what is called paralog distributions. This formalism is described by a system of infinite number of linear equations. We show that this system generates a semigroup of linear operators on the space l ¹. We prove that size distribution of paralogous gene families in a genome converges to the equilibrium as time goes to infinity. Moreover we show that when probabilities of gene removal and duplication are close to each other, then the resulting distribution is close to logarithmic distribution. Some empirical results for yeast genomes are presented.     

Leptospirosis prevalence in Chinese populations in the last two decades

Leptospirosis is a common zoonotic disease in China. From 1991 to 2010, its average annual incidence was 0.70 cases per 100,000 population. During these two decades, three major outbreaks of leptospirosis occurred due to flooding and heavy rainfall. Leptospira interrogans serogroup Icterohaemorrhagiae serovar Lai is the predominant leptospire responsible for at least 60% of Chinese cases, and Apodemus agrarius serves as the major animal host. Based on the differences in predominant leptospiral serovars, epidemic features and incidence, there are three leptospirosis-prevalent regions in China. However, the incidence has significantly decreased in the last ten years.     

A neural net model for epilepsy

A neural net model based in our previous studies with randomly interconnected neural nets is presented here capable of exhibiting epileptic features. These features can be explained in terms of the structural and dynamical properties of the model. In addition, apart from the fact that this model can imitate epileptic phenomena, it might also help to explain some poorly understood clinical phenomena from which general disturbances can produce focal seizures in the brain.     

Branching-diffusion model for the formation of distributional patterns in populations

A continuous time branching-diffusion process model is presented to describe the development of spatial distributional patterns of a biological population. In the model each unit moves independently following diffusion processes on a plane, and multiplies or goes extinct at random times. Standard methods for measuring the degree of aggregation used in field ecology are applied to this model population. Kuno's C _Aindex using quadrat sampling is calculated, and the dependence of the index on time, quadrat size, initial density, and diffusion and branching rules, is discussed. Pielou's index based on distance measurement is evaluated by the solution of a nonlinear partial differential equation. Both methods show that continuous-time branching-diffusion processes produce a contagious spatial pattern; as in a discrete-time model studied by Iwasa and Teramoto (1977).     

Mathematical model for the study of fertility and viability in inbreeding populations

Granted that a single or complex gene is responsible for inbreeding depression, theoretical expressions for fertility and viability are obtained in different diploid populations: brother-sister, half-brother-sister, cousins and double-cousins. The conclusions of the study of viability variations according to the coefficient of parentage are proved by the results of experiments and lead to a new view of genetic load.     

Analysis of genetic control of maize response in anther culture within a diallelic set

The androgenic ability in anther culture in vitro was examined within a diallel set of five maize lines. The complex analysis of genetic variation components, Hayman's diagram, and genetic parameters showed that the anther response is under the control of an additive-dominant genetic system. The examined lines possessed the different correlation of dominant and recessive alleles controlling androgenesis. And 44 was the line with the biggest number of recessive genes, which determined the increase in the trait. The level of dominance varied in different loci, though in the whole the degree of dominance approached to the complete one.     

Emergence and prevalence of human vector-borne diseases in sink vector populations

Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining 'source' populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining 'sink' vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15-55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale.     

A multivariate model for growth of populations

The “random environment” concept is used to model the growth of several interdependent populations. The vital rates are assumed to follow a multi-variate Ornstein-Uhlenbeck process; important properties of this process and of the integrated process (representing log of population growth) are developed. Application to a predator-prey situation is considered and a technique for the estimation of unknown parameters is developed.     

High prevalence of Haemoglobin E in two populations in Assam

Summary Two groups in Assam (India) were examined. Among 80 Khasi (Bhoi subgroup), an austroasiatic tribal group, there were 41% HbE carriers; and in 82 Ahom, a group related to the Thai population, 58% of HbE carriers were found. This high prevalence of HbE in groups with ethnic relations to Southeast Asia supports the contention that the HbE gene was introduced to India from that area.

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Zusammenfassung Zwei Bevölkerungsgruppen in Assam (Indien) wurden untersucht. Bei 80 Khasi (Bhoi-Untergruppe), einem austroasiatischen Stamm, fanden sich 41% HbE-Träger, bei 82 Ahom, Abkömmlingen von Thai-Einwanderern, 58% HbE-Träger. Die große Häufigkeit des HbE in Gruppen mit ethnischen Beziehungen zu Südostasien unterstützen die Ansicht, daß das HbE-Gen von dort nach Indien eingeführt wurde.

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This study was supported by Stiftung Volkswagenwerk.