Genotypic and Phenotypic Characterization of the Drosophila melanogaster Olfactory Mutation Indifferent

Two Drosophila melanogaster third chromosomes carrying the EMS-induced mutations IndifferentA (IndfA) and IndifferentB (IndfB), previously isolated from larvae showing an anosmia when stimulated with nonanol, were recombined with a multi-marked chromosome in order to localize the mutant character(s). Recombinant strains were tested for their larval olfactory responses and classed as either mutant or wild type; both Indf characters were found to be located on the right arm of the chromosome, between ebony and claret. Deletion mapping suggests that the Indifferent wild-type character is a haplo-insufficiency and that IndfA and IndfB are located in cytological region 96A2-7. Deficiencies and both mutant strains were tested with 14 closely related odors (alcohols, acetates, acids and methyl esters, between eight and 10 carbons long). When stimulated with methyl octanoate, IndfA and IndfB appeared recessive; noncomplementation was observed for this phenotype in IndfA/IndfB hybrids indicating that the two characters are allelic. The overall responses of IndfA, IndfB and the deficiencies indicate that Indf is involved in processing organic odors of between eight and 10 carbons in length.

STABILIZING AND DISRUPTIVE SELECTION ON A MUTANT CHARACTER IN DROSOPHILA. IV. SELECTION ON SENSITIVITY TO TEMPERATURE

ABSTRACT Individual selection on temperature sensitivity was applied to the relative length of the 4th vein of the mutant ciD-G in four selection lines according to different selection schemes indicated in Figure 1. These selection systems include, besides the selection on temperature, disruptive selection. In all lines the disruptive component causes an increase of the phenotypic variance, but there are large differences in its composition. The selection changed temperature sensitivity in the expected direction in all lines. In one line (C-D-) however, the change in temperature sensitivity and the increase in variance were only small because the disruptive component and the canalizing component of the selection scheme restricted each others' effect. The results are discussed in relation to earlier results obtained by disruptive selection at one temperature.

Attenuation of virulence inVibrio cholerae

This paper describes the study of a mutant ofVibrio choleraewhich is shown to be attenuated by its avirulence to mouse, rabbit and chick embryo. This mutant character is stable, and the avirulence of this strain probably results from its inability to multiply actively in the tissues of the infected animals. The need for the study of such attenuated strains as live vaccines in man is discussed, and certain aspects of immunity to cholera are reviewed.

The Influence of Selection and Temperature On a Mutant Character (CiD) in Drosophila Melanogaster

Abstract1. In the mutant ciD of Drosophila melanogaster the relative length of the 4th vein was used as a quantitative character. Divergent selection during 30 to 40 generations for long and short vein length was practised in three unrelated base populations. 2. Selection progress continued through about 20 to 30 generations, sometimes with alternating periods of advance and stability. In all three base populations heritability was approximately 0.3, and similar selection limits were reached far beyond the ranges of the base populations. 3. During the course of selection there were striking changes in the appearance of the frequency distributions (bimodality), particularly in the lines selected for a long, i.e. more normal vein. 4. An explanation for this is proposed, which is based on the assumption that the factors (genetic or environmental) influencing the expression of a character are in their effect dependent on the relative length of the vein. Temperature experiments are described which strongly support this hypothesis. Expression, in response to temperature, appeared to be very sensitive to change in a particular expression range. 5. This view implies that vein determination is governed by two at least partially independent genetic systems, one controlling the relative length of the vein and the other relating modifying influences to their phenotypic effects. 6. Thus, the variability in this mutant character seems to be governed in large measure by the properties of its developmental system. 7. The results are discussed in terms of their significance in the fields of quantitative genetics, developmental genetics, and evolution.