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 Long-term selection for a quantitative character in large replicate populations of Drosophila melanogaster: 1. Response to selection

1980 ◽  
Vol 35 (1) ◽  
pp. 1-17 ◽  
Author(s):  
B. H. Yoo
Keyword(s):  
Drosophila Melanogaster ◽  
Phenotypic Variability ◽  
Selection Response ◽  
Quantitative Character ◽  
Response Patterns ◽  
Total Response ◽  
Term Selection ◽  
Bristle Number ◽  
Selection For

SUMMARYThe response to long-term selection for increased abdominal bristle number was studied in six replicate lines of Drosophila melanogaster derived from the sc Canberra outbred strain. Each line was continued for 86–89 generations with 50 pairs of parents selected at an intensity of 20%, and subsequently for 32–35 generations without selection. Response continued for at least 75 generations and average total response was in excess of 36 additive genetic standard deviations of the base population (σA) or 51 times the response in the first generation. The pattern of longterm response was diverse and unpredictable typically with one or more accelerated responses in later generations. At termination of the selection, most of the replicate lines were extremely unstable with high phenotypic variability, and lost much of their genetic gains rapidly upon relaxation of selection.The variation in response among replicates rose in the early phase of selection to level off at approximately 7·6 around generation 25. As some lines plateaued, it increased further to a level higher than would be accommodated by most genetic models. The replicate variation was even higher after many generations of relaxed selection. The genetic diversity among replicates, as revealed in total response, the individuality of response patterns and variation of the sex-dimorphism ratio, suggests that abdominal bristle number is influenced potentially by a large number of genes, but a smaller subset of them was responsible for selection response in any one line.

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 Long-term selection for a quantitative character in large replicate populations ofDrosophila melanogaster: II. Lethals and visible mutants with large effects

1980 ◽  
Vol 35 (1) ◽  
pp. 19-31 ◽  
Author(s):  
B. H. Yoo
Keyword(s):  
Drosophila Melanogaster ◽  
Mutation Rate ◽  
Quantitative Character ◽  
Frequency Of Occurrence ◽  
Term Selection ◽  
Bristle Number ◽  
Selection For ◽  
First Time ◽  
G 14

SUMMARYLethal frequencies on the second and third chromosomes were estimated three times in six replicate lines ofDrosophila melanogasterselected for increased abdominal bristle number, at G 14–16, G 37–44 and G 79. Ten lethals were detected at a frequency of about 5% or higher at G 14–16, of which only one recurred in subsequent tests. Another ten lethals which had not been detected previously were found at G 37–44, and the 5 most frequent ones recurred at G 79. In the last test, 15 presumably new lethals were detected, of which at least 4 appeared well established. In addition, six reversions (fromsctosc+), a new mutant at the scute locus andscawere discovered. The effects on the selected character of some lethals and visible mutants were large and variable, but not always sufficient to explain the observed frequencies. The major lethals detected at G 37–44 and G 79 for the first time were most probably ‘mutations’ (in the broad sense) which occurred during selection. The likely origins of such ‘mutations’ were discussed, with a suggestion that the known mutation rate for recessive lethals would not be incompatible with the observed frequency of occurrence of the ‘mutations’.

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 Long-Term Selection for a Quantitative Character in Large Replicate Populations of Drosophila Melanogaster. V. The Inbreeding Effect of Selection

1980 ◽  
Vol 33 (6) ◽  
pp. 713 ◽  
Author(s):  
BH Yoo
Keyword(s):  
Drosophila Melanogaster ◽  
Quantitative Character ◽  
Relaxed Selection ◽  
Term Selection ◽  
Bristle Number ◽  
Selection For

Four replicate lines of D. melanogaster, which had been selected for increased abdominal bristle number for 58 or 69 generations, were pedigreed for nine generations under selection with or without replacements for failed matings (SW and SO sublines) and under relaxed selection also with or without replacements (RW and RO sublines).

scholarly journals RECOMBINATION AND RESPONSE TO SELECTION IN DROSOPHILA MELANOGASTER

Genetics ◽  
1977 ◽  
Vol 85 (1) ◽  
pp. 125-140
Author(s):  
Vinton Thompson
Keyword(s):  
Drosophila Melanogaster ◽  
Selection Response ◽  
Response To Selection ◽  
Short Term ◽  
Chromosome Recombination ◽  
Suppressed Recombination ◽  
Selection For ◽  
Balancer Chromosomes ◽  
Term Response ◽  
Rate Of Response

ABSTRACT Most biologists believe that recombination speeds response to selection for traits determined by polygenic loci. To test this hypothesis, sixteen Drosophila melanogaster populations were selected for positive phototaxis for twenty-one generations. In some populations, balancer chromosomes were used to suppress autosomal recombination, and in others the autosomes were free to recombine. Suppression of recombination had no effect on mean rate of response to selection, though it may have increased variability in the rate of response among replicate lines. Suppressed recombination lines did not shift selection response to the freely recombining × chromosomes, despite fairly large increases in × chromosome recombination. The results suggest that in populations of moderate size, sex does not accelerate short term response to selection.

SELECTION FOR MALATHION-RESISTANCE IN DROSOPHILA MELANOGASTER

1981 ◽  
Vol 23 (2) ◽  
pp. 355-369 ◽  
Author(s):  
R. S. Singh ◽  
R. A. Morton
Keyword(s):  
Drosophila Melanogaster ◽  
Selection Procedure ◽  
Dominant Trait ◽  
Lower Intensity ◽  
Term Selection ◽  
Modification Factor ◽  
Polygenic System ◽  
Selection For ◽  
High Selection

Results from a long-term selection experiment for malathion-resistance in Drosophila melanogaster are described. A pooled population of 40 locally-caught, iso-female lines was exposed to increasing concentrations of malathion in the food at both a high selection intensity (MH) and a lower intensity (ML). The response was consistent with a polygenic system. Both adult and larval resistance increased in parallel. Changes in the dose-response curve of adults could be approximately described by a dose-modification factor. Larval resistance was more complex; both selected populations showed a maternal effect which could not be explained by sex-linked genes. Larval resistance in the selected populations behaved as a co-dominant trait with respect to the susceptible controls. Adult resistance was dominant in the ML and co-dominant in the MH population, suggesting that different genes conferring resistance were selected. The selection procedure also produced a developmental delay in both populations, dependent on malathion concentration, but present even in its absence.

scholarly journals Studies on the Scutellar Bristles of Drosophila Melanogaster ID. Long-Term Selection for High Bristle Number in Three further Lines Derived From the Oregon-RC Strain, Correlated Responses in Abdominal Bristles, lUld Changes in Regulation of the Scute Locu

1981 ◽  
Vol 34 (3) ◽  
pp. 347
Author(s):  
BL Sheldon ◽  
M K Evanst
Keyword(s):  
Sex Differences ◽  
Drosophila Melanogaster ◽  
Correlated Response ◽  
Correlated Responses ◽  
Term Selection ◽  
Bristle Number ◽  
Selection For

Results of selection over 135 generations for high scutellar bristle number in three further lines derived from Oregon-RC complement those on the four lines reported previously (Sheldon and Milton 1972). All lines differed widely in pattern of scutellar response, correlated response in abdominal and posterior central scutellar bristles, sex differences, and behaviour on relaxing selection, though the selection limits reached in the present three lines were lower than in the previous lines.

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