Dominance, allele frequency and selection in a population of Drosophila melanogaster

1980 ◽  
Vol 208 (1171) ◽  
pp. 163-187 ◽  
Keyword(s):  
Drosophila Melanogaster ◽  
Regression Line ◽  
Inbred Lines ◽  
Negative Slope ◽  
Stabilizing Selection ◽  
Recurrent Parent ◽  
Single Pair ◽  
Two Temperatures ◽  
The Mean ◽  
Half Diallel

The numbers of sternopleural chaetae of 18 inbred lines derived from the Texas population of Drosophila melanogaster were ascertained for flies raised at each of two temperatures, 18 and 25°C. Two characters were then defined: M , the average of the chaeta numbers at the two tempera­tures; and S , half of the difference between the average chaeta numbers at the two temperatures. The inbred lines differed among themselves in both characters, so revealing genetic variation in the Texas population for them both. There was no correlation between the values of M and S among the lines. The mean of the inbred lines did not differ significantly from that of the progenies of 22 single-pair matings among flies taken from the population in either character, so suggesting that the 18 inbred lines provided a fair sample of the genes in the population. The differ­ences between the variances among the inbred lines, on the one hand, and the biparental progenies, on the other, suggested that dominance was present for both characters and that dominant alleles were, in general, present at higher frequencies than their recessive fellows. This was confirmed by a half-diallel experiment with 11 of the 18 inbred lines as parents. The half-diallel further showed that dominance was ambidirectional for character S , but gave no conclusive evidence in this respect for M . The theoretical consequences of ambidirectional dominance combined with higher frequencies of dominant alleles were considered for a simple model involving four loci. This showed, in particular, that when one homozygous line (the recurrent parent) is crossed to a number of other lines (the non-recurrent parents), the amount by which the phenotype of the F 1 exceeds the mean of its two parents shows a regres­sion of negative slope on the phenotype of the non-recurrent parent. The regression line is expected to cut the axis of zero excess at a point that is, on average, as far away from the phenotype of maximum dominance as is the expression of the character in the recurrent parent, but in the opposite direction. The point mid-way between the recurrent parent and the inter­cept thus provides an estimate of the phenotype of maximum dominance. Estimates of the phenotypes of maximum dominance were obtained in this way for both characters, M and S , by means of data from the half-diallel and from a further experiment carried out for the purpose. For character M , the phenotype of maximum dominance does not depart significantly from the mean of the inbreds or from that of the Texas population itself; but, for S , though close to the means, it is significantly higher than them. It is concluded that this type of genetical architecture is to be expected with characters under stabilizing selection and that the phenotype of maximum dominance is the optimal phenotype towards which the selection has been acting.

scholarly journals Modifying the sternopleural hair pattern in Drosophila by selection

1961 ◽  
Vol 2 (1) ◽  
pp. 158-160 ◽  
Author(s):  
E. C. R. Reeve
Keyword(s):  
Drosophila Melanogaster ◽  
Inbred Lines ◽  
The Other ◽  
Absolute Difference ◽  
Mean Absolute Difference ◽  
Quantitative Characters ◽  
Genetic Behaviour ◽  
The Mean ◽  
Left Right Asymmetry ◽  
Two Sides

Two apparently very similar quantitative characters, the numbers of hairs on the sternopleural region and on the abdominal sternites of Drosophila melanogaster, show unexpected differences in their genetic behaviour. In particular, the amount of left-right asymmetry of the sternopleurals (i.e. the mean absolute difference in numbers of hairs on the two sides of the fly) tends to decline when inbred lines are intercrossed, and can be both increased and decreased by straightforward selection; the corresponding index for the sternite hairs—the uncorrelated variance between two sternites, or the mean absolute difference between the numbers of hairs on each—appears, on the other hand, to be susceptible neither to selection nor to change when inbred lines are crossed (Mather, 1953; Reeve & Robertson, 1954; Reeve, 1959).

scholarly journals The effects of stabilizing selection on the time of development in Drosophila melanogaster

1962 ◽  
Vol 3 (3) ◽  
pp. 364-382 ◽  
Author(s):  
Timothy Prout
Keyword(s):  
Drosophila Melanogaster ◽  
Development Time ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Parallel Line ◽  
Total Variance ◽  
Disruptive Selection ◽  
Stabilizing Selection ◽  
Environmental Component ◽  
The Mean

The length of time of development, from oviposition to emergence in Drosophila melanogaster was subjected to stabilizing selection. In each generation only the individuals emerging close to the mean development time were used as parents of the next generation. This line was designated the ‘S’ line. In a parallel line disruptive selection was practised; where in each generation the earliest flies to emerge were mated to the flies last to emerge; those emerging at intermediate times were discarded. This line was designated the ‘D’ line. Two control lines were also carried, where the flies were mated at random with respect to time of emergence. The experiment extended for 40 generations and produced the following results:(1) The variance of development time decreased in the S line and increased in the D line, relative to the control lines.(2) The mean development time decreased in the S line and increased in the D line.(3) The coefficients of variation decreased in the S line and increased in the D line.(4) The viability, measured as per cent flies emerging, decreased in the D line.Toward the end of the experiment the amount of additive genetic variance in the selected lines and in the control lines was estimated from the response to directional selection. The estimates showed that (i) the loss of total variance in the S line can be accounted for completely by a loss in additive genetic variance, and (ii) the increase in the total variance of the D line cannot be ascribed to an increase in the additive genetic variance. It was probably due to an increase in the environmental component of variance, i.e. to a loss of ‘buffering capacity’.

scholarly journals The effect of intraocular pressure on visual field after trabeculectomy in patients with primary open angle glaucoma

2012 ◽  
Vol 59 (1) ◽  
pp. 61-66
Author(s):  
Paraskeva Hentova-Sencanic ◽  
Marija Bozic ◽  
Ivan Sencanic ◽  
Milan Stojcic ◽  
Branislav Stankovic ◽  
...  
Keyword(s):  
Visual Field ◽  
Linear Regression Analysis ◽  
Regression Line ◽  
Visual Fields ◽  
Visual Field Loss ◽  
Rate Of Change ◽  
Negative Slope ◽  
Automated Perimetry ◽  
Percentage Reduction ◽  
The Mean

Purpose: To compare the mean intraocular pres-sure (IOP), peak IOP and percentage reduction in IOP in the first live years following trabeculectomy between the patients with progressed visual field loss and the patients with stable visual fields. Material and methods: Thirty-six eyes of 36 patients were followed for five years after their first trabeculectomy with tonometry and automated perimetry (Octopus 500EZ, program Gl). The rate of change of the visual field was measured by linear regression analysis of the mean sensitivity value (dB9) of each field test versus time (month). Based on the statistical significance of the slope of the regression line (Spear man p value of the correlation coefficient less than 0.05), patients were divided into two groups: with significant negative slope of the regression line (group with progressed visual field loss) and with non-significant slope of the regression line (group with stable visual field). The mean IOP values and percentage of IOP reduction at the end of each of the first live years after surgery were compared between the group with progressed field loss and group with stable fields by using Mann-Whitney U test. Results: Patients with progressed visual field loss had higher mean IOP, higher peak IOP and less reduction in pressure after the operation than patients with stable visual field. The mean IOP at end of the two year postoperative period was significantly higher in patients with progressed visual field loss (21.98?3.38mmHg) than in those with stable fields (17.48?4,80mmHg). The mean percentage reduction in IOP at the end of two year postoperative peri?od was significantly less in patients that showed progression of field loss (21.84%) than in those with stable fields (41.0%). Conclusion: Prognosis for further field loss seems to be better if postoperative pressure is at lower levels and greater percent reduction of IOP is obtained after surgery. The data that predict better prognosis is the mean postoperative IOP value of approximately 18mmHg or less resulting from at least 35% of IOP reduction.

scholarly journals Polygenic mutation in Drosophila melanogaster: the causal relationship of bristle number to fitness.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 861-872 ◽  
Author(s):  
S V Nuzhdin ◽  
J D Fry ◽  
T F Mackay
Keyword(s):  
Drosophila Melanogaster ◽  
Artificial Selection ◽  
Random Mating ◽  
Direct Selection ◽  
Stabilizing Selection ◽  
Fitness Effects ◽  
Bristle Number ◽  
Mean Fitness ◽  
The Mean ◽  
Average Fitness

Abstract The association between sternopleural and abdominal bristle number and fitness in Drosophila melanogaster was determined for sublines of an initially highly inbred strain that were maintained by divergent artificial selection for 150 generations or by random mating for 180 generations. Replicate selection lines had more extreme bristle numbers than those that were maintained without artificial selection at the same census size for approximately the same number of generations. The average fitness, estimated by a single generation of competition against a compound autosome strain, was 0.17 for lines selected for high and low abdominal bristle numbers and 0.19 for lines selected for high and low sternopleural bristle number. The average fitness of unselected lines, 0.46, was significantly higher than that of the selection lines. The fitnesses and the relationships of bristle number to fitness in progeny of all possible crosses of high x high (H x H), high x low (H x L) and low x low (L x L) selection lines were examined to determine whether the observed intermediate optima were caused by direct stabilizing selection on bristle number or by apparent stabilizing selection mediated through deleterious pleiotropic fitness effects of mutations affecting bristle number. Although bristle number was nearly additive for progeny of H x H, H x L and L x L crosses among sternopleural bristle selection lines, their mean fitnesses were not significantly different from each other, or from the mean fitness of the unselected lines, suggesting partly or completely recessive pleiotropic fitness effects cause apparent stabilizing selection. The average fitness of the progeny of H x H abdominal bristle selection lines was not significantly different from the fitness of unselected lines, but the mean fitness of the progeny of L x L crosses was not significantly different from that of the pure low lines. This is consistent with direct selection against low but not high abdominal bristle number, but the interpretation is confounded by variation in average degree of dominance for fitness (on average recessive in the high abdominal bristle selection lines and additive in the low abdominal bristle selection lines). Neither direct stabilizing selection nor pleiotropy, therefore, can account for all the observations.

Whole-Genome Effects of Ethyl Methanesulfonate-Induced Mutation on Nine Quantitative Traits in Outbred Drosophila melanogaster

Genetics ◽  
2001 ◽  
Vol 157 (3) ◽  
pp. 1257-1265 ◽  
Author(s):  
Hsiao-Pei Yang ◽  
Ana Y Tanikawa ◽  
Wayne A Van Voorhies ◽  
Joana C Silva ◽  
Alexey S Kondrashov
Keyword(s):  
Drosophila Melanogaster ◽  
Quantitative Traits ◽  
Spontaneous Mutation ◽  
Developmental Time ◽  
Ethyl Methanesulfonate ◽  
Induced Mutations ◽  
Mean Values ◽  
Eye Color ◽  
Recessive Mutations ◽  
The Mean

Abstract We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to ∼100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20° and by 0.04% at 25°, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.

scholarly journals GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 569-589
Author(s):  
Martin L Tracey ◽  
Francisco J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Natural Population ◽  
Natural Populations ◽  
Genetic Load ◽  
Structural Genes ◽  
Invertebrate Species ◽  
Average Proportion ◽  
Mean Fitness ◽  
The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

Yields of mixtures of single-cross hybrid field beans (Viciafaba L.) with one of the parental inbred lines

1966 ◽  
Vol 67 (2) ◽  
pp. 235-237 ◽  
Author(s):  
D. A. Bond ◽  
J. L. Fyfe ◽  
Gillian Toynbee-Clarke
Keyword(s):  
Inbred Lines ◽  
The Other ◽  
Normal Rate ◽  
Single Cross ◽  
Parental Inbred ◽  
The Mean ◽  
Field Beans

The yields of seed from a hybrid, one of its parents and different mixtures of the hybrid and parent were compared in the case of two different hybrids. Open-pollinated controls were included in the trial, which was sown at about the normal rate for beans. With both hybrids a mixture of 11 of hybrid to 1 of parent yielded as well as the hybrid itself and mixtures of 2 of hybrid to 1 of parent yielded in both cases about 7 cwt./acro more than the mean of the open-pollinated controls. With the higher-yielding hybrid, which had less contrast in vegetative vigour between hybrid and parent, mixtures in the proportions 5:1 and 2:1 showed declining yields, but with the other hybrid they yielded as well as the pure hybrid.

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