scholarly journals Effects of Artificial Selection on Rates of Inbreeding in Populations of Drosophila Melanogaster

1969 ◽  
Vol 22 (1) ◽  
pp. 157 ◽  
Author(s):  
LP Jones
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Artificial Selection ◽  
Selection Intensity ◽  
Base Population ◽  
Next Generation ◽  
Effective Population ◽  
Bristle Number

Three lines from the Canberra base population were selected for increased abdominal bristle number for up to 28 generations with 10 pairs of parents and 20% selection intensity. The effective population size as measured by either variance of family contributions to the next generation or by the rate of inbreeding was gener-ally lowest when the lines were responding rapidly to selection. Consideration of the contributions of families in any generation to the lines five generations later showed that much of the genetic variation came from only few families in some generations.

scholarly journals The effects of X-rays on quantitative characters

1964 ◽  
Vol 5 (3) ◽  
pp. 410-422 ◽  
Author(s):  
G. A. Clayton ◽  
Alan Robertson
Keyword(s):  
Genetic Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Artificial Selection ◽  
Inbred Lines ◽  
X Rays ◽  
Effective Population ◽  
Outbred Population ◽  
Culture Bottle ◽  
Quantitative Characters

1. The rate of production by X-rays of new genetic variation in two quantitative characters in Drosophila melanogaster (sternital and sternopleural bristles) has been investigated, using ‘plateaued’ populations which had reached the limit under artificial selection and, for sternital bristles only, populations which had been made genetically invariant by inbreeding. The genetic variation was always measured by the response of the population to selection. The X-rays dose given in any generation was always 1800 r. to adults.2. Seven plateaued lines had eight cycles of alternate irradiation and selection, each with its non-irradiated control. All the responses were small but in three lines they were significantly greater after irradiation.3. Selection was applied to three different inbred lines, genetically marked to detect contamination, after varying periods of irradiation. At the same time, the inbred lines and lines derived from them which had been mass mated in bottles were selected. The irradiated populations showed a greater response. The new genetic variance produced by the irradiation was approximately 10−5 units/r. The estimate of the dose required to introduce new variation equal to that in a standard outbred population was 500,000 r.4. The effective population size was an important factor in the interpretation of some of these results on the long-term effects of radiation. By observing the variation between replicate lines in the frequency of a gene with a visible effect under these culture conditions (i.e. in a single culture bottle) the effective population size was estimated at sixty. Outbred populations kept under these conditions for many generations showed a reduction of genetic variability in agreement with this value.5. To investigate the possibility that the deleterious genes produced by irradiation would interfere with the response to artificial selection, a standard outbred population was irradiated and selected. In spite of the observed high frequency of recessive lethals produced, the response to selection was very similar to that of the standard population.

scholarly journals Inbreeding in artificial selection programmes

1961 ◽  
Vol 2 (2) ◽  
pp. 189-194 ◽  
Author(s):  
Alan Robertson
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Artificial Selection ◽  
Actual Number ◽  
Effective Population

In a population under artificial selection, the effective population size may be less than the actual number of parents selected because there will be variation between families in the character under selection and consequently in the probability of selection. Expressions are developed for the magnitude of the effect, which will be greater the more intense the selection and the higher the heritability of the selected character. The inbreeding due to outstanding individuals may rise for several generations after their use.

scholarly journals Interrelations between effective population size and other pedigree tools for the management of conserved populations

2000 ◽  
Vol 75 (3) ◽  
pp. 331-343 ◽  
Author(s):  
ARMANDO CABALLERO ◽  
MIGUEL A. TORO
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Genetic Parameters ◽  
Effective Number ◽  
Effective Population ◽  
Clear Cut ◽  
Captive Populations ◽  
Practical Recommendations

Genetic parameters widely used to monitor genetic variation in conservation programmes, such as effective number of founders, founder genome equivalents and effective population size, are interrelated in terms of coancestries and variances of contributions from ancestors to descendants. A new parameter, the effective number of non-founders, is introduced to describe the relation between effective number of founders and founder genome equivalents. Practical recommendations for the maintenance of genetic variation in small captive populations are discussed. To maintain genetic diversity, minimum coancestry among individuals should be sought. This minimizes the variances of contributions from ancestors to descendants in all previous generations. The method of choice of parents and the system of mating should be independent of each other because a clear-cut recommendation cannot be given on the latter.

scholarly journals Allozyme-associated heterosis in Drosophila melanogaster.

Genetics ◽  
1989 ◽  
Vol 123 (4) ◽  
pp. 789-801 ◽  
Author(s):  
D Houle
Keyword(s):  
Drosophila Melanogaster ◽  
Population Size ◽  
Effective Population Size ◽  
Phenotypic Variance ◽  
Effective Population ◽  
Population Mixing ◽  
Stressful Environment ◽  
Genotypic Correlations ◽  
Allozyme Loci ◽  
Growth Characters

Abstract Two large experiments designed to detect allozyme-associated heterosis for growth rate in Drosophila melanogaster were performed. Heterosis associated with allozyme genotypes may be explained either by functional overdominance at the allozyme loci, or closely linked loci; or by genotypic correlations between allozyme loci and loci at which deleterious recessive alleles segregate. Such genotypic correlations would be favored by consanguineous mating, small effective population size, population mixing and strong natural or artificial selection. D. melanogaster is outbred, has large effective population size and there is little evidence for genotypic disequilibria. Therefore it would be unlikely to show allozyme heterosis due to genotypic correlations. In the first experiment I estimated the genotypic values of 97 replicated genotypes. In the second experiment, 500 individuals were raised in a fluctuating, stressful environment. In neither experiment was there any consistent evidence for allozyme heterosis in size or development rate, fluctuating asymmetry for size or in tendency to deviate from the population mean. In the first experiment, heterosis explained less than 5.6% of the genetic variance in growth characters. In the second, heterosis explained less than 0.1% of the phenotypic variance in growth characters. Outside of the molluscs, species which show allozyme heterosis have population structures or histories which tend to promote genotypic correlations. There is little evidence that functional overdominance is responsible for observations of allozyme-associated heterosis.

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