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.

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 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 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 Correlated Responses of Different scute Genotypes to Long-term Selection for Increased Abdominal Bristle Number in Drosophila melanogaster

1974 ◽  
Vol 27 (2) ◽  
pp. 205 ◽  
Author(s):  
BH Yoo
Keyword(s):  
Genetic Background ◽  
Gene Action ◽  
Regression Coefficient ◽  
Dose Effect ◽  
Base Population ◽  
Correlated Responses ◽  
Term Selection ◽  
Bristle Number ◽  
Selection For

The first dose effect of sc+ has been measured for abdominal bristle number in six replicate lines of D. melanogaster being selected upward for this character in the sc homo-and hemizygote. The within-line regression coefficient of the heterozygote on the sc homozygote showed considerable variation among the lines with a range of 0-47-1' 22, indicating the dependence of gene action on genetic background. But, on the average, the effect of sc+ was approximately additive for abdominal bristle number. From this average, the genetic correlation in the base population between the two genotypes was estimated to be considerably less than unity, which suggests some genetic variability that is dependent on the genotype of the major locus. A similar relationship was also obtained for the two male hemizygotes.

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.

Correlated responses in lamb mortality due to long term selection for cannon bone length and fleece medullation in sheep

1983 ◽  
Vol 37 (2) ◽  
pp. 293-299 ◽  
Author(s):  
R. I. Cue
Keyword(s):  
Maximum Likelihood ◽  
Correlated Responses ◽  
Sheep Flock ◽  
Term Selection ◽  
Bone Length ◽  
Selection For

ABSTRACTLamb mortality in a Scottish Blackface hill sheep flock subjected to long term selection for cannon bone length and fleece medullation score was investigated, using maximum likelihood analyses. The selection for cannon bone length and for medullation score had no significant effect on lamb mortality.

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