PubMed Health⌕ Search

Biomedical subjects

T I Axenovich

Publications and source records attributed to T I Axenovich.

13 recordsLinked to original sources
PubMed1999

Segregation analysis of idiopathic scoliosis: demonstration of a major gene effect.

Segregation analysis using a model with age and gender effects was applied to 101 pedigrees ascertained through a proband with idiopathic scoliosis. The transmission probability model was used to detect major gene effect. When we analyzed the pedigrees where affected status was assigned to persons with a Cobb's angle of more than 5 degrees we did not detect a significant major gene effect. However, when the affected status was assigned to persons with pronounced forms of disease only (a curve of at least 11 degrees) a significant contribution of a major causal gene could be established and inheritance could be described according to a dominant major gene diallele model, assuming incomplete sex and age dependent penetrance of genotypes. According to this model, the pronounced forms of idiopathic scoliosis should never occur in the absence of the mutant allele. This indicates that only the carriers of the mutant allele develop pronounced forms of the disease. At the same time, only a fraction of the carriers of the mutant gene should manifest the disease (30% of males and 50% of females).

Adolescent↗
PubMed1998

Inheritance of litter size at birth in the house musk shrew (Suncus murinus, Insectivora, Soricidae).

In this research we estimated the contribution of a major-gene effect to the control of litter size in hybrids between two local populations of the house musk shrew (Suncus murinus). Segregation analysis was performed on the basis of a mixed polygene and major-gene model. The model presumes that two parental populations may differ from each other in gene frequencies and in the values of polygenic effects but not in the major-gene contribution of the trait. Moreover, the peculiarity of the trait--litter size--is taken into account. This trait is not an individual attribute. It characterizes the parental couple and may depend on the genotypes of both parents. Results of segregation analysis of a large hybrid pedigree of Suncus murinus indicate that the parental populations differ in the allele frequency of the major gene (one population is homozygous, while the other contains the two alleles in approximately equal proportions) and in the values of average polygenic effects. Both major-gene and polygenic components are necessary for the correct description of litter size inheritance in interracial hybrids of S murinus, inasmuch as the exclusion of either of them leads to a significant drop in likelihood. The Elston-Stewart criterion also confirms the Mendelian inheritance of the major gene.

Animals↗
PubMed1998

Chromosomal segregation and fertility in Robertsonian chromosomal heterozygotes of the house musk shrew (Suncus murinus, Insectivora, Soricidae).

Crucial to our understanding of chromosomal variation and evolution in mammals are detailed studies of chromosomal heterozygotes, with analyses of chromosomal segregation and chromosome-derived infertility. We studied segregation and fertility in hybrids between karyotypic races of the house musk shrew Suncus murinus. These individuals were heterozygous for up to five Robertsonian fusions (Rbs) and an insertion of heterochromatin in an autosome. All variant chromosomes showed Mendelian segregation and all Rbs segregated independently of each other in the progeny of double heterozygotes. Litter size in single and even multiple Rb heterozygotes was no smaller than that in the less fertile parental strain. The effects of genetic background were more important in determining litter size than Rb heterozygosity for the shrews that we examined.

Animals↗
PubMed1998

Inheritance of male hybrid sterility in the house musk shrew (Suncus murinus, Insectivora, Soricidae).

Two geographic races of the house musk shrew (Suncus murinus) were crossed and intercrossed in the laboratory. Many cases of male sterility were detected among the hybrids. Segregation analysis of the pedigree data showed that the inheritance of male sterility in interracial hybrids of S. murinus can be described within the framework of monogene polyallele model with sterility of a single allele combination. This model is similar if not identical to that proposed by Dobzhansky and Muller.

Alleles↗
PubMed1997

Sample size required for predefined linkage decision quality.

A method for estimating the sample size required to attain a predefined linkage decision quality (type I and type II errors) is proposed using the linkage test power estimate developed by Ginsburg et al. [(1996) Genet Epidemiol 13:355-366]. The method is applicable for samples of arbitrarily structured pedigrees collected via proband. Comparison of different ascertainment schemes and pedigree structures by their consequent minimal sample size was performed. For recessive and dominant inheritance with complete penetrance, the relative ranks of the ascertainment schemes are invariant regardless of the true recombination fraction value and the trait and marker gene frequencies, which enables one to point out the better scheme. The feasibility of evaluating a sampling strategy by the cost of pedigree collection is also considered, and comparison between these two methods of sample planning is performed.

Gene Frequency↗
PubMed1997

Segregation analysis of animal pedigree data from inter-population crosses.

The general method of segregation analysis of pedigree data has been developed and widely used in human genetics. We modified this method to examine pedigree data coming from inter-population crosses. These kinds of pedigrees are common in laboratory and farm animal breeding. This paper describes a rationale for the method and illustrates its application to the study of inheritance of litter size and of male sterility in hybrid stock of the house musk shrew (Suncus murinus) derived from crosses of two geographically isolated populations.

Animals↗
PubMed1996

Prediction of linkage phase by parental phenotypes.

This paper answers the question as to which parental phenotypes are useful in prediction of the linkage phase of the progeny under conditions of linkage equilibrium. I demonstrate that 1) the parents with the same disease status or marker genotype carry no information about phase of the diheterozygous offspring; 2) the linkage phase can be inferred unambiguously only under recessive or dominant control of disease. In any other situations, only the probability of linkage phase is inferred. It has been shown that the relative difference between the probabilities of coupling phase and repulsion phase, epsilon, which is regarded as a measure of accuracy of linkage phase prediction by parental phenotypes, is the same in all informative crosses and is dependent on the genetic model of the disease. Furthermore, epsilon is the same for the di- and polyallelic marker genes.

Alleles↗
PubMed1996

On planning of samples for linkage analysis: two ways of a sample size reduction.

The sample size required for a given type I and type II errors of linkage decision is determined by using the earlier proposed method of the linkage test power estimation [Ginsburg et al., 1996]. Dependence of the sample size on the heterozygotic genotype penetrance is investigated. Two approaches to sample size reduction are considered: the choice of marker gene and the special extension of analyzed pedigree structures. Their effects are quantitatively evaluated in some illustrative situations. It is shown that a practical reduction in sample size can be achieved only when the added part of a pedigree has a special set of phenotypic characteristics in its members.

Genetic Linkage↗
PubMed1996

On estimation of linkage test power.

Two methods of estimating linkage test power are proposed. The first method is based on the maximum likelihood (ML) estimate of the recombination fraction and is intended for use with a likelihood ratio test (LRT) in the form of a chi 2 or lod score. The power is estimated through a noncentral chi 2 distribution with a specially chosen noncentrality parameter. The second method uses the LRT constructed for a simple alternative hypothesis regarding the recombination fraction value. The approximate distribution of this test and a method of estimating its power is proposed. Using simulated pedigree data, the power estimates for these two methods were shown to be satisfactory. Comparisons among these two methods and the computer simulation approach of Boehnke [1986] are performed.

Genetic Linkage↗
PubMed1995

Genetic control of PI and GC variants in the American mink.

Genetic polymorphism of the serum alpha-protease inhibitor (PI) and group-specific component (GC) in minks was revealed using one-dimensional polyacrylamide gel electrophoresis and immunoblotting. Two codominant alleles were identified at each of the two loci. The data ruled out the possibility of any linkage between the PI, GC and the coat colour gene Crystal (Cr).

Animals↗
PubMed1992

A cooperative binomial ascertainment model.

It has been shown that the classical binomial form of ascertainment, assuming a constant probability pi that any affected individual may become a proband for his pedigree, cannot describe a rather wide range of ascertainment procedures that might arise in practice. Some more general heuristic ascertainment formulas might then be preferred, and in this paper we consider the probabilistic basis for these formulas. We retain the binomial assumption of the classical scheme but allow the ascertainment probability to depend on the number of potential probands per pedigree. This probability can be expressed by an increasing or a decreasing function of that number. Various illustrations are given and situations where the "cooperative" binomial scheme should be valuable are discussed.

Mathematics↗