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

Sheldon, B. L.

doi:10.1071/bi9680721

Cited by 8 publications

(11 citation statements)

References 12 publications

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“…Analysis of large base population scores for Oregon-RC in which bristle position was scored (Sheldon 1968), confirms that posterior scutellars are to some extent more strongly canalized than anterior scutellars. The relevant results are as follows:…”

Section: Correlated Responses and Changes In Dominancementioning

confidence: 82%

“…The existence of an anterior-posterior gradient of some kind cannot be denied, but it seems doubtful that changes in bristle number and in degree of canalization around 4 scutellar bristles are simply a composite function of essentially independent anterior and posterior components, as concluded by Scowcroft (1973). Extra bristles in the interstitial position are inexplicable even in the unselected base population in Oregon-RC, where they are nearly half as frequent as extra anteriors in females and almost as frequent as extra anteriors in males (Sheldon 1968). Latt~r and Scowcroft (1970) did not report any appreciable incidence of interstitial bristles in un selected Canberra populations or in two generation selection lines for high anteriors taken from the Canberra population.…”

Section: Correlated Responses and Changes In Dominancementioning

confidence: 99%

“…Sci., 1981,34,347-67. 0004-9417/84/040277$02.00 satisfactorily the results of a range of experiments, most of which involved lines selected for high number of scutellar bristles (Sheldon and Evans 1981). Many experiments have been reported in which no difficulty was experienced in selecting for high number of scutellar bristles starting from a canalized wild-type base population (see Sheldon 1968;Sheldon and Milton 1972;Sheldon and Evans 1981 for reports of their own work and references to other work referred to in the discussion and in Appendix 2). Gibson (1968) concluded from the previous literature that successful selection for low number of scutellar bristles usually involved the presence of a major mutant which reduced the number below four.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, other results from the present authors did tend to support the Gibson (1968) generalization. Sheldon (1968) reported two attempts to establish low-selection lines from an Oregon-RC wild-type stock. In one line virtually no change occurred in frequency of flies with less than 4 bristles over four generations of selection in which a total of 14533 females and 14588 males were scored, so it was discontinued.…”

Section: Introductionmentioning

confidence: 99%

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

Sheldon¹,

Evans²

1984

Aust. Jnl. Of Bio. Sci.

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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.In the early generations of selection, as the mean bristle number slowly dropped below the canalized wild-type level of 4 bristles, flies with more than 4 bristles continued to appear, i.e. the probit width of the 4-bristle class tended to drop from its un selected level of 5·4-5·8". to quite low levels in the selection lines and to recover in the relaxed lines as their mean bristle number moved back towards the un selected level. This could not be interpreted in the same way as similar phenomena in highselection lines, i.e. selection of poor regulators of the scute locus. Other possible explanations for these results and for the new canalization observed at 2 bristles were considered without being able to accommodate them fully within a modified model of regulation of the scute locus. The most likely possibility seems to be that the low selection response is due to selection of less-efficient alleles of a gene which is the inducer of the scute locus. A large reduction in the degree of dominance of sc+ over scute (SCi) was also observed in these selection lines, which may be compatible with the above explanation.Correlated responses in sternital bristle number in the selection and relaxed lines, while generally positive, were not closely related to the pattern of change in scutellar bristles. The dominance of sc+ over SCi in respect of sternital bristles showed little change except in one line where it increased, while dominance in respect of scutellar bristle score decreased.

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Section: Correlated Responses and Changes In Dominancementioning

confidence: 82%

Section: Correlated Responses and Changes In Dominancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Sheldon¹,

Evans²

1984

Aust. Jnl. Of Bio. Sci.

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“…Sheldon (1968) following Rendel et al (1965) and Rendel (1967Rendel ( , 1968Rendel ( , 1969 had held the hypothesis that canalization at four bristles in wild type is accomplished by genetic regulation of the scute locus and that selection for high bristle number merely changed the minor gene background without affecting the canalization genotype. In contrast to this, Sheldon and Milton (1972) interpreted * Part II, Genetics, 1972, 71, 567-95. t Formerly Milton.…”

Section: Introductionmentioning

confidence: 99%

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

Sheldon¹,

Evanst²

1981

Aust. Jnl. Of Bio. Sci.

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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.The early scutellar response supports the conclusion in the previous paper that early selection was mainly for poor regulation of the scute locus at the canalization level of control, since the probit span of the four-bristle class decreased as the mean scutellar number increased in the selection lines, and increased in the relaxed lines as the mean scutellar score decreased.Introduction of the set allele into the selection lines confirmed the earlier findings that the selected background increased scutellar bristles in set to a much lesser extent than in sc+ flies, and that considerable interaction of set and sc+ with selected background occurred. The degree of dominance of sc+ over set was increased in two lines out of five and decreased in one line. The latter indication of breakdown in the dominance level of control was not supported by results of the effect of an extra dose of sc+ in males, where all lines were similar to the unselected level.The correlated response in abdominal bristles was positive, similar in size in the three lines, and smaller than in the previous lines. The changes in abdominal score on relaxation of selection for scutellar bristles do not correlate well with the variable reductions in scutellar score across 10 relaxed lines. Positive, zero or negative genetic correlations between the two characters seem to be possible depending on the line and stage of response. In relation to abdominal scores, changes in dominance of sc+ over set occurred but were not correlated with the dominance changes for scutellar bristles. The effect of an extra dose of sc+ on abdominal bristles was similar in all six lines observed, adding 2·6-4·1 bristles, much smaller than the scutellar effect, where sc+/sc+· Y males exceeded sc+ /sc+ females. _1.1."

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A meristic trait in Drosophila melanogaster x simulans hybrids

Agnew

1973

Genetica

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A quantitative trait, abdominal bristle number, is described in a number of stocks of the two sibling species Drosophila melanogaster and Drosophda simulans and in interspecific hybrids obtained from these stocks. Coefficients of variation for the trait in the parental species and the hybrids are compared, and in the case of the latter are found to fall in the same range as those of the pure species. The results are discussed in the light of previous findings on other bristle systems.

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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

Cited by 8 publications

References 12 publications

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

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

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

A meristic trait in Drosophila melanogaster x simulans hybrids

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