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Biomedical subjects

C F Sing

Publications and source records attributed to C F Sing.

At least 145 records · Page 8Linked to original sources
PubMed1976

Analysis of genetic and environmental sources of variation in serum cholesterol in Tecumseh, Michigan. III. Identification of genetic effects using 12 polymorphic genetic blood marker systems.

Four of 12 unlinked polymorphic marker systems were identified as predictors of normal serum cholesterol levels. Consistent effects between males and females and with other studies suggest that these marker loci are themselves involved in cholesterol determination or are closely linked to the involved loci. Two-locus combinations suggest that an 8-9 mg/100 ml difference in nonfasting serum cholesterol may be predicted between phenotypic classes which are not rare in frequency.

Blood Group Antigens↗
PubMed1975

A consideration of the chi-square test of Hardy--Weinberg equilibrium in a non-multinomial situation.

The multinomial Dirichlet distribution was used to study the effect of correlation between observations in a sample on the frequency of rejection of the Hardy--Weinberg Law when in fact it was true in the population being sampled. It was shown that the usual X2 goodness-of-fit test of Hardy--Weinberg is very sensitive to non-multinomial sampling. In view of the lack of statistical power of the test to detect deviations due to in breeding, it is likely that whenever H--W is rejected using samples of size 100 or less, the underlying causation is sample correlation rather than failure of the H--W law to be true. Related to these findings is, of course, the effect of pooling heterogeneous frequencies or, in the case of contingency tables, Simpson's paradox (see Simpson, 1951).

Gene Frequency↗
PubMed1975

Analysis of genetic and environmental sources of variation in serum cholesterol in Tecumseh, Michigan. I. Analysis of the frequency distribution for evidence of a genetic polymorphism.

Analyses of serum cholesterol measurements on 4,619 males and 4,730 females residing in the community of Tecumseh, Michigan, were conducted to estimate the contribution of sex, age, temporal variation, and bimodality to determining the normal variation among individuals sampled without regard to their health status. Female values had a higher mean (2.8 mg/100 ml greater) but smaller variance than males when adjusted by polynomial regression to a common age. Positive skew in the frequency distribution for both sexes was removed by natural logarithm (ln) transformation. Age variation accounted for 28.5% and 29.4% of the variance in a ln cholesterol measurement of males and females, respectively. Between 7% and 10% of the variance in a ln cholesterol value was estimated to be attributable to differences between age-adjusted replicate measurements of the same individual. The reduction in individual variability by adjustment for these contributions to variance will allow a more precise evaluation of the relative contribution of alternate genetic hypotheses as explanations for normal variation in cholesterol. Assuming bimodality, approximately one in 1,000 males and one in 1,000 females belong to a second mode of hypercholesterolemic individuals. The locus determining familial hypercholesterolemia is not a major source of normal phenotypic variation in the Tecumseh population.

Adolescent↗
PubMed1974

A model for analysis of population structure.

Arguments have been presented for the appropriateness of a multinomial Dirichlet distribution for describing single-locus genotypic frequencies in a subdivided population. This distribution is defined as a function of allele frequency, the average (over the entire population) inbreeding coefficient and the correlation between genotypes within a subdivision. Alternative parameterizations and their genetic interpretations are given.-We then show how information from a sample drawn from this subdivided population, in the absence of pedigrees, can be combined with the multinomial Dirichlet model to form a likelihood function. This likelihood function is then used as the basis for estimation and testing hypotheses concerning the genetic parameters of the model. Comparisons of this approach to the alternative procedure of Cockerham (1969) and (1973) are made using human data obtained from Tecumseh, Michigan and Monte Carlo simulations.-Finally, implications of these results to statistical inference and to mutation rates are presented.

Alleles↗
PubMed1973

Inherited biochemical variation in Drosophila melanogaster: noise or signal? I. Single-locus analysis.

A study was conducted using small effective population size as an experimental design to test selective neutrality of seven isozyme polymorphisms. Loci varied as to the degree to which the decay of heterozygosity over 21 generations was retarded. Selection for heterozygotes, overdominance, is implicated for at least four of seven loci. Of these ADH gave the largest heterozygote excess in the presence of inbreeding. An interaction between the small population size treatment and excess heterozygosity suggests that (1) the loci studied may be selectively neutral and linked to other loci which are under the influence of selection or (2) the selection coefficients for the loci studied are not independent of the background genotype. In either case four of the seven enzymes studied are signaling the operation of selection. The problem of distinguishing the effect of a single marker from that of a chromosome segment is emphasized. The identification of the genetic unit of selection is crucial to any interpretation of the meaning of enzyme polymorphisms.

Alcohol Oxidoreductases↗
PubMed1969

Studies of isozyme patterns in nullisomic-tetrasomic combinations of hexaploid wheat.

Thirty-eight wheat strains, each nullisomic for one chromosome and tetrasomic for a homoeologous (related) one, were analyzed electrophoretically for 12 different enzymes, and a gene (or genes) for alkaline phosphatase was localized to chromosomes 4B and 4D. The other 11 enzymes showed no significant electrophoretic variation. The fact that the only mutants observed affect the same enzyme favors the concept that rigorous selection operates in the polyploids both to preserve certain types of variants and to eliminate others.

Journal Article↗