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Biomedical subjects

A E Stark

Publications and source records attributed to A E Stark.

14 recordsLinked to original sources
PubMed1980

Sex differences in the inheritance of some anthropometric characters in twins.

Biometrical genetical techniques have been applied to the analysis of certain anthropometric characters measured in 134 pairs of adult twins. After allowing for assortative mating it appears that there is a family environment (E2) component for variation in height larger than previously reported. "Fatness" traits - weight, ponderal index, and skinfold thickness - all show higher heritabilities in males and substantial E2 components in females, and reasons for this are discussed. The same is true for cephalic index and forearm length but the reason for these differences is not so obvious. Head length shows a much higher heritability than head breadth. A larger sample of DZ opposite-sex pairs would allow more powerful discrimination, but the variety of patterns of variation revealed by the model-fitting approach used here justify its use over more traditional techniques.

Anthropometry↗
PubMed1977

A model of assortative mating with partial dominance.

A model of assortative mating incorporating partial dominance is proposed for a single locus with two alleles. It is derived by starting from an arbitrary genotypic distribution and finding symmetric and non-selective mating frequencies which duplicate this distribution. Numerical values are imputed to genotypes, the homozygotes having numerically equal values, opposite in sign, and the heterozygote having a value determined by the gene and heterozygote frequencies. The model is specified in a canonical form which reveals the correlation between mates based on genotypic values, and relates the correlation to the fixation index. It permits negative as well as positive values of the fixation index. It is shown that this general model includes several particular cases, in equilibrium phase, occurring in the literature.

Alleles↗
PubMed1977

Comments on the Penrose-Stanton model of assortative mating.

A single-locus model of assortative mating proposed by Penrose and extended by Stanton is analysed. It is shown that the formulae giving values of correlations between males and relatives derived by Stanton apply to a general class of symmetric, non-selective mating schemes in equilibrium when genotypes have additive values. The canonical form of Stanton's system is derived, revealing that the assignment of additive values of genotypes does not apply also to the canonical vectors.

Crosses, Genetic↗
PubMed1976

Hardy-Weinberg law: asymptotic approach to a generalized form.

The equilibrium frequencies of a generalized Hardy-Weinberg law are approached at a geometric rate under assortative mating, irrespective of the initial genotypic frequencies. The asymptotic form is similar to that of Wright, and the pattern of assortative mating is based on deviations from the mean genotypic value.

Gene Frequency↗
PubMed1976

A model for assortative mating.

It is shown that a generalization of the Hardy-Weinberg law of the proportions of genotypes of the kind given by Wright (1922) is maintained in equilibrium by a pattern of assortative mating suggested by Fisher (1918) and elaborated by Malécot (1939, 1948).

Genetics, Population↗
PubMed1976

On the method of Penrose of estimating the number of effective factors contributing to a character.

Penrose (1969) presented a method of estimating the number of effective factors contributing to a quantitative character. The method uses samples of parent-child and sib-sib phenotypic values. More detailed mathematical analysis shows that his assertions regarding the method are correct under the assumptions which he made, provided that his phrase 'the same quantitative effect' is interpreted to mean 'makes an equal contribution to the variance'.

Alleles↗
PubMed1971

Bayes' theorem.

Explore the source record for details and available documents.

Counseling↗
PubMedDate not supplied

A twin study of skin reflectance.

Skin colour has been measured by reflectance spectrophotometry on 134 pairs of twins at three sites, forehead, forearm and upper arm, each at three wavelengths, 425, 545 and 685 nm. Tanning is measured most reliably at 685 nm and at this wavelength the heritability is high at the least exposed upper arm site, intermediate on the forearm, while on the forehead variation is entirely environmentally determined. The same gradient is observed, through less strikingly at 545 nm, but at 425 nm, where haemoglobin is reflecting most of the light, the degree of genetic determination is the same at all sites.

Adolescent↗
PubMedDate not supplied

Marital correlation for anthropometric characteristics in Brazilian Indians.

A total of 336 couples from 10 villages of three Brazilian Indian tribes was studied in relation to 15 anthropometric characteristics. Correlation coefficients between husband and wife were generally positive, none of the negative ones reaching a probability level of 1% or less. Thirteen correlations attained this level, but none of the traits behaved similarly in the three tribes. Height adjustment taking into consideration the correlation between mates for age did not much alter the correlation coefficients, but a larger influence was observed after allowance for temporal effects. A significant pair of canonical variables was obtained considering sitting height and leg length, but factors related to facial and bone form, extracted through principal-components analysis, yielded correlations insignificantly different from zero.

Anthropometry↗