Discrete Phenotypes Research Articles

Urinary pepsinogen isozymes: a highly polymorphic locus in man.

A genetic analysis of human urinary pepsinogen isozymes is presented. Nine discrete phenotypes were identified in a population survey of 215 unrelated Caucasian individuals. The phenotypes were characterized by differences among the staining intensities of the activated group I pepsinogens, Pg 5, Pg 4, Pg 3, and Pg 2. The genetic studies demonstrated that the codominant expression of four alleles, PgA, PgB, PgC and PgD, at a single genetic locus determined the nine phenotypes identified. Linkage analysis excluded close linkage of the Pg locus with the chromosome 6 markers HLA, GLO1, and Bf.

The diagnosis of zygosity in twins.

Uniovular and diovular twin pairs can be classified with at least 90% accuracy by careful questioning or by ratings by observers of similarity in appearance, eye color, ear conformation, and the like. This article outlines the methods required for highly accurate zygosity diagnosis using blood typing, fingerprints, and anthropometry. The logic behind the use of discrete Mendelian phenotypes is explained and tables are provided which give the odds against a dizygotic twin pair showing concordance on eight blood group systems, four serum proteins, and six red blood cell enzymes. These tables are suitable for use with American twins of European ancestry; the method of generating such tables is explained so that similar tables based on different gene frequency estimates or for additional genetic markers can be easily constructed. The logic behind the use of metric, polygenic traits in zygosity diagnosis is also presented, together with tables giving the odds against a dizygotic twin pair showing various degrees of similarity in ponderal index, in cephalic index, and in Slater's Z score, a measure of fingerprint similarity. Taken together, the 18 serological markers should misclassify dizygotic twins as monozygotic fewer than two times in 1000. With the three anthropometric variables, this average probability of misclassification drops about 1 order of magnitude.

Preferential mating. Nonrandom mating of a continuous phenotype

A phenotypically determined nonrandom mating model is specified for a continuous trait controlled by a major gene. The distribution of phenotypic preferences of any particular individual choosing a mate may be specified in terms of the phenotype of the individual. The relative mating frequency is dependent on the frequency of the genotypes. Conditions for equilibria, polymorphic and degenerate, are given for a series of analytical and numerical cases. Certain classical nonrandom mating models for discrete phenotypes are special cases of the preferential mating model. However, other discrete phenotypic models do not have parallels because either the intergenotypic relationships are not geometrically consistent or the selective and assortative properties are not phenotypically consistent.

Genetic fine structure of the albino (al) region ofNeurospora crassa

SUMMARYBy crossing a pair of albino strains each with a different adjacent nutritional marker and then crossing the same pair of albino markers with the nutritional markers transposed it was possible to order a series ofalmutants with a resolution approaching that available for nutritional markers. A genetic map with approximated distances is provided demonstrating a grouping of mutant sites for a range of discrete carotenoidless phenotypes.