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Biomedical subjects

C S Haley

Publications and source records attributed to C S Haley.

82 records · Page 5Linked to original sources
PubMed1985

Lack of congruence of S-carboxymethyl-L-cysteine sulphoxidation and debrisoquine 4-hydroxylation in a Caucasian population.

One-hundred-and-twenty volunteers and three families were investigated for possible association between the sulphoxidation of S-carboxymethyl-L-cysteine and the debrisoquine hydroxylation polymorphism. The observed individual variations in these two metabolic reactions were shown not to be concordant (rs = 0.068) and any heritable factors controlling the major aspects of these phenomena do not co-segregate.

Adolescent↗
PubMed1984

Detecting sex-associated variation with the families of MZ and DZ twins.

Phenotypic variation in human population may contain contributions from a number of different sex-associated genetic influences. These influences include maternal effects, the effects of sex-linked loci, and the effects of sex-limited autosomally linked loci. The families produced by MZ and DZ twins provide statistics which permit the detection and estimation of these effects. In particular, they provide statistics derived from various types of age-matched half-sibs and cousins in addition to those derived from the more usually studied full-sib or parent-offspring relationships. Specific models for genetic maternal effects, sex-linkage and sex-limitation are used to explore the use of extended twin design for the detection of and the discrimination between various sex-associated effects. The sample sizes required to detect maternal effects and sex-linkage were considered for some simple cases and it is concluded that comparison derived from the progeny of twins will often provide better tests for these effects than those derived from parent-offspring comparison.

Family↗
PubMed1984

Genetic aspects of the polymodally distributed sulphoxidation of S-carboxymethyl-L-cysteine in man.

Interindividual variation in the sulphoxidation of S-carboxymethyl-L-cysteine (750 mg p.o.) was investigated in 200 healthy volunteers. Nearly a 100-fold difference was observed between individuals with respect to the amount of sulphoxide metabolites detected in their 0-8 h urine (0.6 to 59.1% recovery). Such a difference was shown to be reproducible over several months in 40 subjects who spanned the entire range of capacities. Cumulative plots and maximum likelihood analysis of the distribution indicated that a bimodal model was most probable. Analysis of pedigree data obtained from 12 families suggested a genetic effect with overlying environmental influences.

Adolescent↗
PubMed1983

The genetical response to natural selection by varied environments. II. Observations on replicate populations in spatially varied laboratory environments.

From each of two populations of Drosophila melanogaster, collected two months previously, from Chateau Tahbilk, S. Australia and Groningen, The Netherlands, duplicate populations were initiated in each of four environments which differed in their degree of environmental heterogeneity. Differing combinations of three food media based on oatmeal/treacle, potato or fig were used to simulate levels of environmental heterogeneity within the populations. The polymorphic loci, Adh, Est-6, G-6pdh, alpha-Gpdh, Pgm, Lap-D and Aph in both the Chateau Tahbilk and Groningen derived populations and 6Pgdh, which was only polymorphic in the populations which came from Chateau Tahbilk, were monitored in the experiment. The populations maintained a size of about 2500 adults and were sampled after 16 and 32 generations. Large changes of phenotype frequency were shown by all loci. Despite a frequent divergence of phenotype frequencies between duplicate cages, systematic effects of occasion and environment were present and allele frequencies at many loci were shown to be changing at a faster rate than could be due to random genetic drift. Genetic heterozygosity differed between environments but was not positively correlated with degree of environmental heterogeneity.

Animals↗
PubMed1981

The monozygotic twin half-sib method for analysing maternal effects and sex-linkage in humans.

The influence of maternal effects and sex-linked loci upon the statistics derived from an analysis of the families of monozygotic twins (the so called MZ half-sib design of Nance and Corey, 1976) is examined. If, as in the published analyses, the progeny sexes are considered jointly, maternal effects and sex-linkage may be confused. In the absence of sex-linkage a comparison of maternal and paternal half-sib covariances will often be a more powerful test for maternal effects than the conventional comparison of maternal and paternal parent-offspring covariances. If the progeny sexes are considered separately the analysis of sex-linkage presents no fundamental problems.

Female↗
PubMed1981

The advantages of analysing human variation using twins and twin half-sibs and cousins.

The "twin family" design is a new strategy for studying quantitative characters in man which overcomes most limitations of earlier designs and which is readily accessible to existing twin research units as it uses only adult twins (both identical and non-identical) and their spouses and offspring and juvenile twins (both identical and non-identical) and their parents. The design yields all information inherent in ordinary twin studies but also permits the simultaneous estimation of more components than any other design. Tests for most genetical and environmental components of variation and the assumptions of the design are provided. Particular advantages are the unambiguous separation of sex-linkage and maternal inheritance, the analysis of the mechanism of assortative mating and the specification of more realistic environmental models. Although several components are confounded the biases are not seriously misleading. However, it would be necessary to include adoption data to resolve the effects of cultural transmission which are otherwise confounded with the family environment. Nevertheless, this design provides a wealth of data on a diversity of relationships and promises to be a valuable tool for the analysis of individual differences in man.

Environment↗
PubMedDate not supplied

A linkage map of pig chromosome 10.

Despite the large number of mapped markers along the pig genome, many chromosomes remain poorly covered. One reason for this problem is the lack of shared markers between separate mapping projects. We describe localized map integration by mapping selected markers from the United States Department of Agriculture map onto the European consortium map. Such integration of physical and genetic mapping information has enabled us to assign and orient a linkage map that extends over most of pig chromosome 10.

Animals↗
PubMedDate not supplied

Selective genotyping for QTL detection using sib pair analysis in outbred populations with hierarchical structures.

A simulation study illustrates the effects of the inclusion of half-sib pairs as well as the effects of selective genotyping on the power of detection and the parameter estimates in a sib pair analysis of data from an outbred population. The power of QTL detection obtained from samples of sib pairs selected according to their within family variance or according to the mean within family variance within half sib family was compared and contrasted with the power obtained when only full sib pair analysis was used. There was an increase in power (4-16% ) and decrease in the bias of parameter estimates with the use of half-sib information. These improvements in power and parameter estimates depended on the number of the half sib pairs (half sib family size). Almost the same power as that obtained using all the available sib pairs could be achieved by selecting only 50-60% the animals. The most effective method was to select both full and half sib pairs on the basis of high within full sib family variance for the trait in question. The QTL position estimates were in general slightly biased towards the center of the chromosome and the QTL variance estimates were biased upwards, there being quite large differences in bias depending on the selection method.

Journal Article↗
PubMedDate not supplied

A simple and rapid method for calculating identity-by-descent matrices using multiple markers.

A fast, partly recursive deterministic method for calculating Identity-by-Descent (IBD) probabilities was developed with the objective of using IBD in Quantitative Trait Locus (QTL) mapping. The method combined a recursive method for a single marker locus with a method to estimate IBD between sibs using multiple markers. Simulated data was used to compare the deterministic method developed in the present paper with a stochastic method (LOKI) for precision in estimating IBD probabilities and performance in the task of QTL detection with the variance component approach. This comparison was made in a variety of situations by varying family size and degree of polymorphism among marker loci. The following were observed for the deterministic method relative to MCMC: (i) it was an order of magnitude faster; (ii) its estimates of IBD probabilities were found to agree closely, even though it does not extract information when haplotypes are not known with certainty; (iii) the shape of the profile for the QTL test statistic as a function of location was similar, although the magnitude of the test statistic was slightly smaller; and (iv) the estimates of QTL variance was similar. It was concluded that the method proposed provided a rapid means of calculating the IBD matrix with only a small loss in precision, making it an attractive alternative to the use of stochastic MCMC methods. Furthermore, developments in marker technology providing denser maps would enhance the relative advantage of this method.

Animals↗