scholarly journals Selection for Canalization of the Scute Phenotype in Drosophila Melanogaster

1960 ◽  
Vol 13 (1) ◽  
pp. 36 ◽  
Author(s):  
JM Rendel ◽  
BL Sheldon
Keyword(s):  
Drosophila Melanogaster ◽  
Wild Type ◽  
Bristle Number ◽  
Selection For ◽  
High Selection

Selection for low variance of scutellar bristle number in scute flies resulted in canalization about a mean of two bristles. Selection for high variance appeared ineffective. The sensitivity of high selection lines to changes in temperature at which the flies were reared was much greater than the sensitivity of the low selection lines and the sensitivity of wild�type cultures.

scholarly journals Studies on The Scutellar Bristles of Drosophila Melanogaster I. Basic Variability, Some Temperature and Culture Effects, and Responses to Short-Term Selection in the Oregon-Rc Strain

1968 ◽  
Vol 21 (4) ◽  
pp. 721 ◽  
Author(s):  
BL Sheldon
Keyword(s):  
Drosophila Melanogaster ◽  
Major Gene ◽  
Selection Response ◽  
Wild Type ◽  
Short Term ◽  
Term Selection ◽  
Bristle Number ◽  
Selection For ◽  
High Selection ◽  
Culture Effects

The results of short runs of disruptive and high selection for scutellar bristles in wild-type Drosophila are explained in terms of the hypothesis that canalization at four bristles is due to regulation of the major gene in the developmental system (Rendel, Sheldon, and Finlay 1965). Selection response has probably been due to selection for modifier (minor) genes rather than for isoalleles of the major gene or weak regulator alleles. Some environmental effects on the character, short runs of selection for low bristle number or different bristle types, and effects of relaxing selection are also reported.

scholarly journals Selection for and against a canalized phenotype in Drosophila melanogaster

1967 ◽  
Vol 10 (1) ◽  
pp. 21-33 ◽  
Author(s):  
S. S. Y. Young
Keyword(s):  
Drosophila Melanogaster ◽  
Lower Proportion ◽  
Modifier Genes ◽  
Wild Type ◽  
Appreciable Change ◽  
Bristle Number ◽  
Alternative Hypotheses ◽  
Males And Females ◽  
Selection For ◽  
Relative Change

Selection for and against the canalized phenotype in scutellar bristles was attempted in two selection lines and a randomly selected line was used as control. The selection lines were the Decanalization line (D) and the Canalization line (N). The D line was maintained by matings of scute males (scwbl) with three scutellars with wild-type females (scwbl/yw) with five bristles, in the N line scute males with four bristles were mated with wild-type females also with four bristles, while in the C line males and females of the above genotypes were selected at random. The lines were established from a sample of flies taken from a line selected for high scutellar numbers.After eighteen generations of selection the C line was characterized by a regression of mean bristle number without appreciable change in variance. Relative to the N line, the D population showed a lower proportion of flies having four scutellars, a higher variance in bristle numbers, and a higher proportion of four-bristle scute flies having abnormal patterns.Two alternative hypotheses were advanced to account for the results of this experiment. The first postulated a relative change in the widths of the four-bristle canalization zones in the selection lines, while the second suggested a relative change in frequencies of specific modifier genes for scutellars in scute and in wild-type genotypes of the lines. The evidence favours the latter hypothesis.

scholarly journals A quantitative genetic analysis of fitness and its components in Drosophila melanogaster

1986 ◽  
Vol 47 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Trudy F. C. Mackay
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Populations ◽  
Strongly Correlated ◽  
Wild Type ◽  
Relative Contribution ◽  
Quantitative Characters ◽  
Quantitative Genetic ◽  
Bristle Number ◽  
Metric Traits ◽  
Average Fitness

SummaryForty-one third chromosomes extracted from a natural population of Drosophila melanogaster were assessed for net fitness and for the quantitative characters viability, net fertility, female productivity, male weight, abdominal bristle number, and sternopleural bristle number. Net homozygous and heterozygous fitness of the third chromosomes was estimated by competition against a marked balancer third chromosome. Average fitness of the homozygous lines relative to wild-type heterozygotes was 0·13, indicating substantial inbreeding depression for net fitness. All significant correlations of quantitative characters with fitness and with each other were high and positive. Homozygous fitness is strongly correlated with net fertility, viability, and female productivity, moderately associated with male weight, and not significantly associated with bristle traits. The combination of metric traits which best predicts homozygous fitness is the simple multiple of viability and female productivity. Heterozygous fitness is not correlated with homozygous fitness; furthermore, the relative contribution of metric traits to fitness in a heterozygous population is likely to be different from that deduced from homozygous lines. These observations are consistent with a model of genetic variation for fitness in natural populations caused by segregation of rare deleterious recessive alleles.

scholarly journals Studies on the Scutellar Bristles of Drosophila melanogaster. IV. Selection for Low Bristle Number in Oregon-RC Wild-type Lines

1984 ◽  
Vol 37 (4) ◽  
pp. 277
Author(s):  
BL Sheldon ◽  
M K Evans
Keyword(s):  
Recessive Gene ◽  
Population Level ◽  
Initial Response ◽  
The Other ◽  
Selection Line ◽  
Base Population ◽  
Wild Type ◽  
Threshold Phenomenon ◽  
Bristle Number ◽  
Selection For

Results are presented of 130-145 generations of selection for low scutellar bristle number in four lines of D. melanogaster derived directly from an Oregon-RC wild-type stock and in one derived from an Oregon-RC line selected for low sternital bristle number. The most rapid initial response and the lowest mean scutellar bristle number ultimately reached, just below 2 bristles, occurred in a line in which the response was due to a new recessive gene located at approximately 17�4 on the X chromosome. Three of the other four lines reached a plateau just above a mean of 2 bristles after different patterns of response. These plateaux reflected a new canalization or threshold phenomenon at 2 bristles in these lines. The remaining line reached a mean of about 2� 5 bristles after some 50 generations and remained at that level or slightly higher thereafter, but had no indication of canalization at 2 bristles. Two relaxed lines were derived from each selection line at different times and showed variable patterns of regression towards the base population level.

scholarly journals Action-based attention in Drosophila melanogaster

2019 ◽  
Vol 121 (6) ◽  
pp. 2428-2432 ◽  
Author(s):  
Giovanni Frighetto ◽  
Mauro A. Zordan ◽  
Umberto Castiello ◽  
Aram Megighian
Keyword(s):  
Drosophila Melanogaster ◽  
Visual Target ◽  
Motor Program ◽  
Action Selection ◽  
Wild Type ◽  
Fundamental Process ◽  
Directed Action ◽  
Selection For ◽  
First Time ◽  
Selection For Action

The mechanism of action selection is a widely shared fundamental process required by animals to interact with the environment and adapt to it. A key step in this process is the filtering of the “distracting” sensory inputs that may disturb action selection. Because it has been suggested that, in principle, action selection may also be processed by shared circuits in vertebrate and invertebrates, we wondered whether invertebrates show the ability to filter out “distracting” stimuli during a goal-directed action, as seen in vertebrates. In this experiment, action selection was studied in wild-type Drosophila melanogaster by investigating their reaction to the abrupt appearance of a visual distractor during an ongoing locomotor action directed to a visual target. We found that when the distractor was present, flies tended to shift the original trajectory toward it, thus acknowledging its presence, but they did not fully commit to it, suggesting that an inhibition process took place to continue the unfolding of the planned goal-directed action. To some extent flies appeared to take into account and represent motorically the distractor, but they did not engage in a complete change of their initial motor program in favor of the distractor. These results provide interesting insights into the selection-for-action mechanism, in a context requiring action-centered attention, that might have appeared rather early in the course of evolution. NEW & NOTEWORTHY Action selection and maintenance of a goal-directed action require animals to ignore irrelevant “distracting” stimuli that might elicit alternative motor programs. In this study we observed, in Drosophila melanogaster, a top-down mechanism inhibiting the response toward salient stimuli, to accomplish a goal-directed action. These data highlight, for the first time in an invertebrate organism, that the action-based attention shown by higher organisms, such as humans and nonhuman primates, might have an ancestral origin.

scholarly journals The response to artificial selection from new mutations in Drosophila melanogaster.

Genetics ◽  
1991 ◽  
Vol 128 (1) ◽  
pp. 89-102 ◽  
Author(s):  
A Caballero ◽  
M A Toro ◽  
C López-Fanjul
Keyword(s):  
Drosophila Melanogaster ◽  
Single Mutation ◽  
Effective Population ◽  
Environmental Variance ◽  
Epistatic Interactions ◽  
Bristle Number ◽  
Population Sizes ◽  
Selection For ◽  
Mutational Variance ◽  
New Mutations

Abstract Twenty generations of divergent selection for abdominal bristle number were carried out starting from a completely homozygous population of Drosophila melanogaster. All lines were selected with the same proportion (20%) but at two different numbers of selected parents of each sex (5 or 25). A significant response to selection was detected in eight lines (out of 40) and, in most cases, it could be wholly attributed to a single mutation of relatively large effect (0.5-2 phenotypic standard deviations). The ratio of new mutational variance to environmental variance was estimated to be (0.33 +/- 0.11) X 10(-3). The distribution of mutant effects was asymmetrical, both with respect to bristle number (85% of it was negative) and to fitness (most detected bristle mutations were lethal or semilethal). Moreover, this distribution was leptokurtic, due to the presence of major genes. Gene action on bristles ranged from additive to completely recessive, no epistatic interactions being found. In agreement with theory, larger responses in each direction were achieved by those lines selected at greater effective population sizes. Furthermore, the observed divergence between lines selected in opposite directions was proportional to their effective size, as predicted for mutations of large effect.

Chromatin structure of a P-element-transduced hsp-28 gene in Drosophila melanogaster

1986 ◽  
Vol 6 (11) ◽  
pp. 4126-4129
Author(s):  
J C Eissenberg ◽  
S C Elgin
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Chromatin Structure ◽  
Dnase I ◽  
P Element ◽  
Direct Selection ◽  
Wild Type ◽  
Dnase I Hypersensitive Sites ◽  
Hypersensitive Sites ◽  
Selection For

The Drosophila hsp-28 gene was heat inducible when transduced to novel chromosomal sites even when no direct selection for transduced gene expression was imposed. The pattern of DNase I-hypersensitive sites 5' to the wild type and transduced copy of hsp-28 was similar. In addition, DNase I-hypersensitive sites occurred within the P-element sequences flanking transduced loci.

scholarly journals Decanalization of scutellar bristle number in Drosophila

1971 ◽  
Vol 17 (2) ◽  
pp. 95-101 ◽  
Author(s):  
W. R. Scowcroft ◽  
B. D. H. Latter
Keyword(s):  
Marked Reduction ◽  
Test System ◽  
Developmental Stability ◽  
Base Population ◽  
Wild Type ◽  
X Ray ◽  
Bristle Number ◽  
Selection For ◽  
Two Populations

SUMMARYA major difference in developmental stability has been demonstrated between two populations produced by artificial selection for supernumerary scutellar bristles. The test system involves the substitution of an X-ray induced partial revertant of sc1 for the wild-type allele at the scute locus, enabling direct comparisons to be made of the degree of canalization at the wild-type level of expression of the character. One population is comparable with the unselected Canberra stock in stability, though it differs appreciably in mean bristle number: the other population shows a marked reduction in the level of regulation of bristle number variability. The alleles responsible for the reduced level of canalization are rare in the base population, and are of particular importance in the determination of limits to directional selection. Their effects on developmental stability have been shown to depend on the activity of the allele at the scute locus.

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