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Now showing items 1 - 6 of 6

  • Predictive Model and Software for Inbreeding-Purging Analysis of Pedigreed Populations

    Garcia-Dorado, A.   Wang, J.   Lopez-Cortegano, E.  

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  • The purge of genetic load through restricted panmixia in a Drosophila experiment

    Avila, V.   Amador, C.   Garcia-Dorado, A.  

    Using Drosophila melanogaster, we explore the consequences of restricted panmixia (RP) on the genetic load caused by segregating deleterious recessive alleles in a population where females mate a full sib with probability about 1/2 and mate randomly otherwise. We find that this breeding structure purges roughly half the load concealed in heterozygous condition. Furthermore, fitness did not increase after panmixia was restored, implying that, during RP, the excess of expressed load induced by inbreeding had also been efficiently purged. We find evidences for adaptation to laboratory conditions and to specific selective pressures imposed by the RP protocol. We discuss some of the consequences of these results, both for the evolution of population breeding structures and for the design of conservation programmes.
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  • On the genetic parameter determining the efficiency of purging: an estimate for Drosophila egg-to-pupae viability

    Bersabe, D.   Garcia-Dorado, A.  

    The consequences of inbreeding on fitness can be crucial in evolutionary and conservation grounds and depend upon the efficiency of purging against deleterious recessive alleles. Recently, analytical expressions have been derived to predict the evolution of mean fitness, taking into account both inbreeding and purging, which depend on an effective purging coefficient (de). Here, we explore the validity of that predictive approach and assay the strength of purging by estimating de for egg-to-pupae viability (EPV) after a drastic reduction in population size in a recently captured base population of Drosophila melanogaster. For this purpose, we first obtained estimates of the inbreeding depression rate (d) for EPV in the base population, and we found that about 40% was due to segregating recessive lethals. Then, two sets of lines were founded from this base population and were maintained with different effective size throughout the rest of the experiment (N = 6; N = 12), their mean EPV being assayed at different generations. Due to purging, the reductions in mean EPV experienced by these lines were considerably smaller than the corresponding neutral predictions. For the 60% of d attributable to nonlethal deleterious alleles, our results suggest an effective purging coefficient de > 0.02. Similarly, we obtain that de > 0.09 is required to roughly account for purging against the pooled inbreeding depression from lethal and nonlethal deleterious alleles. This implies that purging should be efficient for population sizes of the order of a few tens and larger, but might be inefficient against nonlethal deleterious alleles in smaller populations.
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  • On the Use of the Classical Tests for Detecting Linkage

    Garcia-Dorado, A.   Gallego, A.  

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  • Accumulation of deleterious mutations: Additional Drosophila melanogaster estimates and a simulation of the effects of selection

    Caballero, A.   Cusi, E.   Garcia, C.   Garcia-Dorado, A.  

    We report an assay of egg-to-adult viability in full-sibling mutation accumulation (MA) lines derived from a completely homozygous population of Drosophila melanogaster and maintained for 210 generations. A simultaneous evaluation was also made of a large population derived from the same origin and maintained as a control for the same period. We also present computer simulations to explore the possible decline in viability of the control population due to mutation accumulation and the possible effect of selection within and between MA lines. For this purpose, we used two mutational models independent from the data analyzed and based on radically different assumptions. The first model implies a large number of mutations of small effect, whereas the second implies a much smaller number of mutations with much larger effects. The observed rate of decline in mean viability was very small but significant (0.077%). The rate of increase in among line variance (0.189X10-3) was similar to those obtained previously in the same lines. The simulation results indicated that a model of many mutations of small effect is incompatible with the evolution of the mean viability of the control and MA lines over generations, the distribution of line means after 210 generations of mutation accumulation, and the pattern of line extinction over generations. Basically, this model predicted a large drop in viability, both in the control and particularly the MA lines, that is not observed empirically. It also predicted a rate of line extinction too low in the early generations and too high in the later ones. In contrast, the model based on few mutations of large effect was generally consistent with all the observations.
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  • Mitral valve prolapse secondary to right ventricular enlargement in patients with pulmonary hypertension after toxic rapeseed oil ingestion


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