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Biomedical subjects

R Chakraborty

Publications and source records attributed to R Chakraborty.

At least 235 records · Page 13Linked to original sources
PubMed1982

Inheritance of digital arches in humans: is the major gene fully penetrant?

From the fingertip pattern analysis of 125 families with 376 children from Velanadu Brahmin and 100 families with 286 children from Telaganya Brahmin caste sects of Andhra Pradesh, India, the occurrence of an arch on at least one of the ten finger tips is shown to be aggregated in families. The mode of aggregation is in conformity with a major dominant gene with 0.28 chance of penetrance. This is to some extent contradictory to the result published from the analysis of a single Habbanite Jewish pedigree. Some implications of this discordant result are also discussed.

Child↗
PubMed1982

Transmission of the PiZ allele for alpha 1-antitrypsin deficiency: population genetic considerations.

It is shown that a simple preferential transmission of the PiZ allele by PiZ-heterozygous males for alpha 1-antitrypsin deficiency cannot maintain the observed polymorphism at the locus without invoking any viability or fertility selection against the PiZ gene carriers (heterozygotes or homozygotes). From the data on frequencies of PiZ alleles in Europe, the estimates of such selection coefficients are shown to be of the order of 5-20%, which seems too large for natural populations. Furthermore, an analysis of 26 nuclear families, each ascertained through a heterozygous PiZ or homozygous ZZ child, does not provide statistical evidence for such a hypothesis.

Alleles↗
PubMed1982

Problems in the assessment of relative risk of chronic disease among biological relatives of affected individuals.

A question often asked in regard to a chronic disease is whether the risk to a biological relative of a case is evaluated, and if so by how much the risk is altered. To answer this question, data may be collected directly with genetic objectives in mind by ascertaining population of pedigrees. More often, the initial assessment of the question comes from family history data collected in an incidental manner in the course of a case-control or similar type of study. This paper discusses some limitations to the inferences which can be derived from such casual family history data. These include (i) poor statistical properties of standard relative risk measures, (ii) interpretational problems of observed relative risks when affected cases arise from genetic as well as nongenetic causes and when genes may not always be expressed in individuals in whom they are present, and (iii) confounding effects which may occur when a high risk allele alters the age of onset pattern of the disease. These problems result largely from a loss of design control over the degree of exposure of individuals ascertained and can lead to a small observed relative risk value even when genetic factors are important. Suggestions for handling such casual family history data are offered.

Age Factors↗
PubMed1981

The St. Lawrence Island Eskimos: genetic variation and genetic distance.

The Eskimos of St. Lawrence Island have been typed for genetic variation at 44 discrete genetic loci. Three private polymorphisms, at the 2,3-diphosphoglycerate mutase, peptidase B, and purine nucleoside phosphorylase loci, have been observed, which may be useful in future studies of genetic relationships between Eskimos and other circumpolar populations. Genetic distance analysis reveals a close relationship between the St. Lawrence Island Eskimos and other Eskimo populations and that the Eskimo populations form a distinct cluster from Amerindian populations. The St. Lawrence Island Eskimos appear to be more similar to Asiatic Eskimos than to other groups. Caucasian admixture in this population is estimated to be between 2 and 7%.

Alaska↗
PubMed1981

A simple test for the aggregation of disease occurrence in genealogical data.

A simple test for the aggregation of occurrence of a trait in genealogical data is given; a test criterion is developed, and the power of the test to detect aggregation of risk is computed. The test utilizes pairs of individuals between whom transmission of risk factors may occur. As long as aggregation is reasonably strong and prevalence not too low, only modest amounts of data are required. It provides an easy and inexpensive first examination of data which can reveal whether the effort required to conduct more elaborate genealogical studies and analysis is warranted.

Genetic Diseases, Inborn↗
PubMed1981

Use of odds of paternity computations in determining the reliability of single exclusions in paternity testing.

In parentage determination with genetic markers the concept of paternity index is used to evaluate the relative likelihood of fathership of an accused male individual. When a battery of genetic tests are performed, the event of inadvertant technical errors or the occurrence of suppressor genes that cause an apparent paternity exclusion of the male concerned reduces this likelihood to zero. However, through a study of statistical properties of the paternity index statistic based on the other genetic systems, it is possible to examine the reliability of one or a few such apparent exclusions. The details of this approach is examined here by analytical methods following the statistical principles of likelihood ratio test procedures. Some illustrative data are also analyzed to show the practical utility of this approach.

Alleles↗
PubMed1980

A test for the radomness of the occurrence of a disease trait in familial or other similar ordered sequences of epidemiological data.

Through the construction of a probability distribution, a test is proposed for the randomness of the occurrence of an epidemiological event in a series of structured ordered sequences. Such sequences may be of persons admitted to hospital in some specified order, individuals seen in a large set of extended screening program, or individuals in a large set of extended genealogies. Modifications to account for the limited length of ascertained sequences are also given. The method will be particularly important in the first-stage evaluation of genealogical data to indicate the existence and degree of familial aggregation of diseases such as cancer and to justify more complex methods of analysis designed to evaluate the specific elements of causation that may be operating. The statistical power of this approach is also derived, considering the anticipated sample sizes in its application, to detect some forms of familial aggregation in a large genealogical data base from Laredo, Texas.

Age Factors↗
PubMed1980

Genetic structure of Pileolaria pseudomilitaris (Polychaeta: Spirorbidae).

The genetic structure of Pileolaria pseudomilitaris was studied by means of gene-diversity analysis of allozyme frequencies. At an esterase locus, most of the gene diversity was due to subdivision of the population into colonies and subpopulations separated by less than 100 meters. Gene frequencies at a phosphoglucose isomerase locus were similar over many kilometers, but differed between two habitat types. Differences between colonies are attributed to drift and founder effect; similarities over greater distances are attributed to similar selection pressures. A mathematical appendix details the method of gene diversity analysis for a multi-leveled, hierarchically subdivided population.

Animals↗
PubMed1980

Relationship between single- and multi-locus measures of gene diversity in a subdivided population.

A mathematical relationship between the coefficient of gene diversity as derived from average single locus statistics and Smouse and Spielman's multi-locus measure is established under the assumption of linkage equilibrium in a substructured population. A formula for estimating the average time of split of subpopulations from such gene diversity is also derived for the multi-locus criterion. Unlike the estimate derived for single-locus criterion, this estimate does not explicitely depend on the number of subpopulations. The method is illustrated with data on allozyme studies from the South American Indian populations.

Alleles↗
PubMed1980

Comparing the "family set" approach to estimate heritability with other conventional estimators: a Monte Carlo simulation.

A Monte Carlo simulation is performed to study the distribution of the family set estimators of heritability and to compare their performance with that of some conventional estimators used in human genetics. Comparisons of statistical properties among the two family set estimators (one based on the partial regression coefficients of the index's values on those of sib and cousin, respectively, and one based on the variances of the differences between the phenotypic values of index and cousin and of index and sib) and the three conventional estimators (one based on regression of index value on midparental value, another based on the sib-sib correlation, and the last one based on the index-cousin correlation) are also made under two genetic models.

Analysis of Variance↗