Curt Stern

Model Estimates of the Number of Gene Pairs Involved in Pigmentation Variability of the Negro-American

This note presents revised model derivations for pigmentation distributions in the Negro-American. Instead of the formerly accepted estimate of 30% Caucasian alleles the recent estimate of 20% has bee

A PROPOSED STANDARD SYSTEM OF NOMENCLATURE OF HUMAN MITOTIC CHROMOSOMES

Abstract The following statement has been drawn up by a study group, which met to formulate an agreed system of nomenclature for human chromosomes, with a view to eliminating the confusion which has arisen from the independent publication of a variety of systems by different workers.

THE DEVELOPMENTAL AUTONOMY OF EXTRA SEX COMBS IN DROSOPHILA MELANOGASTER.

Abstract In males of Drosophila melanogaster the first legs possess a sex comb, certain tibial transverse rows of bristles, and certain basitarsal transverse rows. These structures are absent on the second and third legs. The recessive autosomal mutant esc (extra sex comb) transforms certain features of the second and third into those of first legs. In different legs the transformation may be incomplete. The different parts may be transformed independently of each other, resulting in an array of partially transformed legs which are epigenetic mosaics of changed and unchanged areas. Genetic mosaics consisting of esc esc patches on esc + legs were obtained in consequence of X-ray induced somatic crossing over. By means of a translocation the esc esc areas were marked by genetically yellow pigmentation on the background of wild-type esc + . In the genetic mosaics esc acts autonomously in causing the appearance of sex combs and both types of transverse rows even in very small esc esc areas. Wild-type colored sex comb teeth on second and third legs were induced by X-ray irradiation of esc + males. The second legs of males with the combination esc D en +en of esc d , a dominant allele of esc, and en (engrailed) had a typical (primary) sex comb as well as the secondary comb normally placed by en on the first leg only. The gene esc as compared to esc+ controls the terminal pattern of leg differentiation by changing the competence of imaginal disk cells to respond to a prepattern that is alike for both alleles. The changed response consists in a tendency in certain areas toward growth in a transverse direction coupled with differentiation in a closely packed row, of bristles or teeth.

The genetic control of developmental competence and morphogenetic tissue interactions in genetic mosaics

Summary1.InDrosophila melanogaster the genotype Theta causes the development of an interalar bristle-organ which is not formed in the wild type. The genotype Minute-n causes, in Theta flies, a strong reduction in the frequency of the occurrence of the interalar bristle.2.By means of genetic mosaics, produced by somatic crossing over and segregation, a developmental analysis was applied to the differences in interalar differentiation between the wild-type, the Theta and the Minute-n genotype.3.Loss of Minute-n in segregated tissues of Minute-n Theta flies leads to differentiation of the interalar bristle. Loss of Minute-n and Theta in segregates of such flies may also lead to differentiation of the bristle, particularly in spots of small area.4.In the neighborhood of the border between the genetically different tissues of mosaics extra bristles may be formed.5.The data furnish evidence for interactions between the genetically different tissues of mosaics: inhibition of bristle formation in the surroundings of differentiating bristles, and spread of gene-dependent substances concerned with differentiation.6.The results can be interpreted in terms of a constant prepattern for the interalar bristle in wild-type, Theta and Minute Theta genotypes, but of different competence of cells with the three genotypes to respond to the prepattern by differentiation of the interalar bristle.

The Determination of Sterility in Drosophila Males Without a Complete Y-Chromosome

It has been known that males of Drosophila melanogaster with an incomplete Y-chromosome produce morphologically normal but immobile and degenerating spermatozoa. This sterility is not due to the genetic constitution of the gametes. It is shown by means of transplantations of sterile testes into fertile larvae and of fertile testes into sterile larvae that the sterility is either caused by early localized somatic influences on the developing gametes or is an autonomous gametic property due to predetermination in the diploid phase.

Die genetische Analyse der Chromosomen

ZusammenfassungWir fassen unsere genetische Analyse der Chromosomen zusammen: Im ersten Teil wurde gezeigt, daß eine wichtige Folgerung aus der allgemeinen Chromosomentheorie der Vererbung, die Gleichheit der Zahl der Koppelungsgruppen und der nicht miteinander homologen Chromosomen, erfüllt wird. Der zweite Abschnitt brachte einen Beweis für die qualitative genetische Verschiedenheit der einzelnen Teile eines Chromosoms. Im letzten Teil wird die Realität der linearen Anordnung der Gene in den Chromosomen nachgewiesen.

Über Chromosomenelimination bei der Taufliege

Bestimmte Mosaikbildungen bei der Taufliege lassen sich dadurch erklaren, das Teile des 3. Chromosoms in einigen Zellen eliminiert worden sind.ZusammenfassungBestimmte Mosaikbildungen bei der Taufliege lassen sich dadurch erklären, daß Teile des 3. Chromosoms in einigen Zellen eliminiert worden sind.

Determination of bristle direction in Drosophila

Abstract In Drosophila melanogaster the recessive mutant aristaless ( al ) leads to an abnormal orientation of the posterior scutellar bristles. The mutant also affects the shape of the dorsal scutellar surface. Heterozygous al + al flies show more than 10% penetrance in causing mutant-type bristle orientation. By means of genetic mosaics on the scutellum, caused by X-ray-induced somatic crossing-over and marked by areas of yellow pigmentation on a nonyellow background, it is shown that al autonomously leads to abnormal scutellar growth. Secondarily, in cases of such abnormal growth, an aristaless-type direction is imposed on the posterior scutellar bristle, regardless of its own al al or al + al genotype.

Fortschritte der Chromosomentheorie der Vererbung

Die Chromosomentheorie der Vererbung besagt, das die aus den Vererbungsexperimenten erschlossenen Einheiten, die das Erscheinen erblicher mendelnder Eigenschaften bedingen, die sogenannten Erbanlagen, Erbfaktoren, Faktoren oder Gene, in den Chromosomen liegen oder irgendwie mit ihnen materiell verbunden sind. Das Verhalten, die Verteilung und Kombination der Chromosomen beim Ubergang von einem Elternindividuum zu einem Individuum der nachsten Generation soll also den Mechanismus darstellen, der die in den genetischen Versuchen sichtbar werdende Verteilung und Kombination der Erbfaktoren bedingt.

The cell lineage of the sternopleura in Drosophila melanogaster

Abstract Larvae of Drosophila melanogaster were irradiated with X-rays to induce somatic crossing over resulting in genetically marked mosaic areas. Mosaic sternopleural sclerites were associated with mosaic mesonta in frequencies compatible with random association. Association of mosaic sternopleurae and mosaic legs was significantly more frequent than accountable by chance. It is concluded that the sternopleura is always derived from the ventral, not from the dorsal, disk. Apparently differing results of earlier authors are reinterpreted in terms of embryonic indetermination as contrasted to larval determination of prospective imaginal areas.