QUANTITATIVE GENETIC ANALYSIS OF DIVERGENCE IN MALE SECONDARY SEXUAL TRAITS BETWEEN DROSOPHILA SIMULANS AND DROSOPHILA MAURITIANA.

The sibling species Drosophila simulans and D. mauritiana differ significantly in a number of male secondary sexual traits, providing an ideal system for genetic analysis of interspecific morphological divergence. In the experiment reported here, F hybrids from a cross of two inbred lines were backcrossed in both directions and about 200 flies from each backcross were scored for several traits (bristle numbers and cuticle areas), as well as 18 markers distributed throughout the genome.

An introgression analysis of quantitative trait loci that contribute to a morphological difference between Drosophila simulans and D. mauritiana.

Drosophila simulans and D. mauritiana differ markedly in morphology of the posterior lobe, a male-specific genitalic structure. Both size and shape of the lobe can be quantified by a morphometric variable, PCl, derived from principal components and Fourier analyses.

Molecular dissection of a major gene effect on a quantitative trait: the level of alcohol dehydrogenase expression in Drosophila melanogaster.

A molecular mapping experiment shows that a major gene effect on a quantitative trait, the level of alcohol dehydrogenase expression in Drosophila melanogaster, is due to multiple polymorphisms within the Adh gene. These polymorphisms are located in an intron, the coding sequence, and the 3' untranslated region. Because of nonrandom associations among polymorphisms at different sites, the individual effects combine (in some cases epistatically) to produce "superalleles" with large effect.

Genetic analysis of a morphological shape difference in the male genitalia of Drosophila simulans and D. mauritiana.

Two closely related species of Drosophila, D. simulans and D. mauritiana, differ markedly in morphology of the posterior lobe of the male genital arch.

A genome-wide survey of hybrid incompatibility factors by the introgression of marked segments of Drosophila mauritiana chromosomes into Drosophila simulans.

In hybrids between Drosophila simulans and D. mauritiana, males are sterile and females are fertile, in compliance with HALDANE's rule. The genetic basis of this phenomenon was investigated by introgression of segments of the mauritiana genome into a simulans background.

Differences in crossover frequency and distribution among three sibling species of Drosophila.

Comparisons of the genetic and cytogenetic maps of three sibling species of Drosophila reveal marked differences in the frequency and cumulative distribution of crossovers during meiosis. The maps for two of these species, Drosophila melanogaster and D. simulans, have previously been described, while this report presents new map data for D.

Effects of a transposable element insertion on alcohol dehydrogenase expression in Drosophila melanogaster.

Variation in the DNA sequence and level of alcohol dehydrogenase (Adh) gene expression in Drosophila melanogaster have been studied to determine what types of DNA polymorphisms contribute to phenotypic variation in natural populations. The Adh gene, like many others, shows a high level of variability in both DNA sequence and quantitative level of expression. A number of transposable element insertions occur in the Adh region and one of these, a copia insertion in the 5' flanking region, is associated with unusually low Adh expression.

The effect of an intronic polymorphism on alcohol dehydrogenase expression in Drosophila melanogaster.

Several lines of evidence indicate that natural selection controls the frequencies of an allozyme polymorphism at the alcohol dehydrogenase (Adh) locus in Drosophila melanogaster. However, because of associations among sequence polymorphisms in the Adh region, it is not clear whether selection acts directly (or solely) on the allozymic site. This problem has been approached by using in vitro mutagenesis to distinguish among the effects on Adh expression of individual polymorphisms.

Determinants of stability in the perception of subjective contours.

The present study constituted an initial experimental effort to examine the fragmentation characteristics of subjective contours within the photopic and upper scotopic ranges of illumination. Four stimulus factors known to influence the visibility of subjective contours-target luminance, inducing area size and contrast, and contour orientation--were examined. Results indicated that subjective contours are indeed unstable perceptual phenomena.

Patterns of naturally occurring restriction map variation, dopa decarboxylase activity variation and linkage disequilibrium in the Ddc gene region of Drosophila melanogaster.

Forty-six second-chromosome lines of Drosophila melanogaster isolated from five natural populations were surveyed for restriction map variation in a 65-kb region surrounding the gene (Ddc) encoding dopa decarboxylase (DDC). Sixty-nine restriction sites were scored, 13 of which were polymorphic. Average heterozygosity per nucleotide was estimated to be 0.

Sustained attention and the Type A behavior pattern: the effect of daydreaming on performance.

The present study examined the ability of Type A and Type B subjects to sustain attention during a 40-min visual vigilance task. It was predicted that Type A subjects would perform better than Type B subjects and that the performance of both groups would be related to the frequency of daydreams during the vigil. Type A subjects outperformed Type B subjects with regard to perceptual sensitivity (A') and number of signal detections.

Use of in vitro mutagenesis to analyze the molecular basis of the difference in Adh expression associated with the allozyme polymorphism in Drosophila melanogaster.

In natural populations of Drosophila melanogaster, the alcohol dehydrogenase (Adh) locus is polymorphic for two allozymes, designated Slow and Fast. Fast homozygotes generally have a two- to threefold higher ADH activity level than Slow homozygotes for two reasons: they have a higher concentration of ADH protein and the Fast protein has a higher catalytic efficiency. DNA sequencing studies have shown that the two allozymes generally differ by only a single amino acid at residue 192, which must therefore be the cause of the catalytic efficiency difference.

Associations between DNA sequence variation and variation in expression of the Adh gene in natural populations of Drosophila melanogaster.

A large part of the genetic variation in alcohol dehydrogenase (ADH) activity level in natural populations of Drosophila melanogaster is associated with segregation of an amino acid replacement polymorphism at nucleotide 1490, which generates a difference in electrophoretic mobility. Part of the allozymic difference in activity level is due to a catalytic efficiency difference, which is also caused by the amino acid replacement, and part is due to a difference in the concentration of ADH protein. A previous site-directed in vitro mutagenesis experiment clearly demonstrated that the amino acid replacement has no effect on the concentration of ADH protein, nor does a strongly associated silent polymorphism at nucleotide 1443.

Comparison of alcohol dehydrogenase expression in Drosophila melanogaster and D. simulans.

Alcohol dehydrogenase (ADH) gene expression was analyzed in Drosophila melanogaster and its sibling species D. simulans. The levels of ADH activity, ADH-cross-reacting material (CRM), and ADH-mRNA were analyzed for several strains of each species, which derive from diverse geographic locations around the world.

Genetic basis of the difference in alcohol dehydrogenase expression between Drosophila melanogaster and Drosophila simulans.

Drosophila melanogaster and its sibling species, Drosophila simulans, differ in expression of the enzyme alcohol dehydrogenase (ADH). Adult melanogaster flies that are homozygous for the Slow allozyme have approximately twice the level of ADH activity and crossreacting material as simulans adults. There is no corresponding difference in ADH mRNA, however, so this difference in ADH protein level is evidently due to a difference in the rate of translation of the two RNAs and/or to a difference in protein stability.

Genetic characterization of dipeptidase activity modifiers in Drosophila melanogaster from natural populations.

An examination of Drosophila melanogaster from natural populations revealed genetic variation for dipeptidase-A (DIP-A) and dipeptidase-B (DIP-B) activities within sets of lines that differed from one another only in the second or the third chromosome. Analyses of diallel crosses indicate that both activities are inherited additively, and coordinate control of expression is suggested by the significant positive correlation between the two activities. Electrophoresis and thermal denaturation studies failed to detect structural differences among lines with different levels of DIP-A activity.

Quantitative analysis of RNA produced by slow and fast alleles of Adh in Drosophila melanogaster.

The alcohol dehydrogenase (ADH) locus (Adh) of Drosophila melanogaster in polymorphic on a world-wide basis for two allozymes, Fast and Slow. This study was undertaken to determine whether the well-established difference in ADH protein concentration between the allozymes is due to a difference in mRNA levels. RNA gel blot hybridization and an RNase protection assay were used to quantify ADH mRNA levels.

The relationship between dipeptidase activity variation and larval viability in Drosophila melanogaster.

The enzyme dipeptidase-A (DIP-A) in Drosophila melanogaster is coded by a second chromosome locus that is polymorphic for three allozymes in natural populations. DIP-A appears to be the only enzyme in D. melanogaster capable of hydrolyzing the dipeptide glycyl-L-isoleucine, since flies homozygous for null alleles at this locus have no detectable glycyl-L-isoleucine-ase activity.

Stimulus context and infant orientation discrimination.

In three experiments, the effect of additional "contextual" elements on the discrimination of the orientation of linear and curvilinear segments was investigated with 4-month-old infants. In Experiment 1, paired visual matrices (one which contained some irregularity in orientation of internal elements, vs one which contained no irregularities) were presented. Infants detected irregular matrices significantly better than chance, but such detection was not aided by contextual elements.