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  • 1
    Electronic Resource
    Electronic Resource
    Forward and reverse response to artificial selection (1976)
    Springer
    Theoretical and applied genetics 48 (1976), S. 101-104 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of t ′ generations of reverse selection after t generations of forward selection can be described by expressing the change in the metric mean resulting from reverse selection (R) interms ofthe change in the metric mean due to the previous forward selection (Δx). An additive model of artificial selection in a population of effective size N with no natural selection has been considered. If reverse selection is continued for as many generations as the previous forward selection (t′=t), then the ratio R/Δx equals 1 − F where F is the inbreeding coefficient for a neutral locus at generation t and is estimated as [1−(1−1/2N)t]. The result of a single generation of reverse selection (t′=1) following t generations of forward selection can be described in terms of the ratio NR1/ηDx where R1 is the response to the first generation of reverse selection. The value of NR1/Δx is expected to be (1−F) /2F. For any period of reverse selection following any period of forward selection, the value of R/Δx never exceeds t ′/t, and tends to decrease exponentially from this value as t increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00281652
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of selection on the standardized variance of gene frequency (1976)
    Springer
    Theoretical and applied genetics 48 (1976), S. 263-268 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of directional and heterotic selection on the standardized variance of gene frequency (f=σ q 2 /¯q(1−¯q)) has been examined. It has been found that heterotic selection always results in f values lower than those expected due to drift alone. Additive directional selection can result in low f values, but values larger than those expected due to drift will be observed under additive selection with low initial gene frequency, or when the populations have been separated for a very long period of time in which case f expected due to drift is quite high (around 0.7 or greater). The effect of selection on f is unlikely to be detected if the observed value of f is less than 0.1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264957
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  • 3
    Electronic Resource
    Electronic Resource
    Direct and correlated responses to selection for post-weaning weight gain on ad libitum or restricted feeding in mice (1982)
    Springer
    Theoretical and applied genetics 63 (1982), S. 145-150 
    Details
    ISSN: 1432-2242
    Keywords: Mice ; Selection ; Growth rate ; ad libitum feeding ; Restricted feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Selection for post-weaning weight gain in mice from 21 to 42 days, on either a full or restricted feeding level during this period was carried out for seven generations. Control lines were maintained for each feeding level. The rate of selection response was higher on full feeding due to a higher heritability and a larger phenotypic variance. Realised heritabilities of 0.29±0.05 and 0.19±0.04 for selection on full and restricted feeding respectively, were in close agreement with base population estimates. Selection on full feeding led to positive correlated responses in 21 day weight, 42 day weight, food intake and efficiency between 21 and 42 days, and 42 day tail length, but with little change in reproductive performance. Correlated responses to selection on restricted feeding were reduced 21 day weight, but an increase in 42 day weight and increased efficiency from 21 to 42 days. However, overall reproductive performance fell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303697
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  • 4
    Electronic Resource
    Electronic Resource
    The sampling variance of the correlation coefficients estimated from two-fold nested and offspring-parent regression analyses (1972)
    Springer
    Theoretical and applied genetics 42 (1972), S. 97-100 
    Details
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A formula is presented for the large-sample variance of phenotypic, genetic and environmental correlation coefficients, estimated from two-fold nested genetic analyses of balanced or unbalanced offspring data. Where parents of these offspring are scored, offspring on parent regression estimates of genetic parameters may be obtained for each parental level of the nested model. The large-sample variance of the offspring-parent genetic correlation coefficients, computed from either level or by using mid-parent data, is given. The first formula is a correction and generalisation of an expression given by Grossman (1970), while the second formula is an extension of a relationship derived by Reeve (1955).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583409
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  • 5
    Electronic Resource
    Electronic Resource
    The conflict between natural and artificial selection in finite populations (1980)
    Springer
    Theoretical and applied genetics 56 (1980), S. 57-64 
    Details
    ISSN: 1432-2242
    Keywords: Homeostatic natural selection ; Artificial selection ; Finite populations ; Selection plateau
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A single locus model of the interaction between natural selection and artificial selection for a quantitative character in a finite population, assuming heterozygote superiority in natural fitness but additive action on the character, has been studied using transition probability matrices. If natural selection is strong enough to create a selection plateau in which genetic variance declines relatively slowly, then the total response to artificial selection prior to the plateau will be much less than that expected in the absence of natural selection, and the half-life of response will be shorter. Such a plateau is likely to have a large proportion, if not all, of the original genetic variance still present. In selection programmes using laboratory animals, it seems likely that the homozygote favoured by artificial selection must be very unfit before such a plateau will occur. A significant decrease in population fitness as a result of artificial selection does not necessarily imply that the metric character is an important adaptive character. These implications of this model of natural selection are very similar to those derived by James (1962) for the optimum model of natural selection. In fact, there seems to be no aspect of the observable response to artificial selection that would enable anyone to distinguish between these two models of natural selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264426
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  • 6
    Electronic Resource
    Electronic Resource
    Long-term selection for a quantitative character in large replicate populations of Drosophila melanogaster (1980)
    Springer
    Theoretical and applied genetics 57 (1980), S. 113-117 
    Details
    ISSN: 1432-2242
    Keywords: Long-term selection ; Relaxed selection ; Reverse selection ; Dominance of bristle number genes ; Drosophila melanogaster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reverse and relaxed selection were carried out in sublines which were derived from six replicate lines of Drosophila during 86–89 generations of selection for increased abdominal bristle number, and the reverse selection sublines were reciprocally crossed with selection lines of their origin. The results of serial relaxed selection initiated at different generations of selection confirm that the accelerated responses observed in the selection lines were largely due to deleterious genes, particularly lethals, with large effects on the selected character. The decline in mean bristle number under relaxed selection was not much different between crowded and uncrowded relaxed sublines. Reverse selection initiated at generation 57 was very effective, though it failed to bring the mean back to the base population level, and the genetic differences between replicate sublines (two from each of the six lines) indicate that low bristle number genes were probably rare in the selection lines. The genes which were still segregating after 57 generations of selection, on the average, did not show any directional dominance. The contribution of the X-chromosome to selection response was proportional to its chromosome length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00253881
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  • 7
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    Online Mendelian Inheritance in Animals (OMIA): a comparative knowledgebase of genetic disorders and other familial traits in non-laboratory animals (2003)
    Oxford University Press
    Details
    Publication Date: 2003-01-01
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 8
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    Molecular basis of a new ovine model for human 3M syndrome-2 (2020)
    BioMed Central
    Details
    Publication Date: 2020-09-15
    Description: Background Brachygnathia, cardiomegaly and renal hypoplasia syndrome (BCRHS, OMIA 001595–9940) is a previously reported recessively inherited disorder in Australian Poll Merino/Merino sheep. Affected lambs are stillborn with various congenital defects as reflected in the name of the disease, as well as short stature, a short and broad cranium, a small thoracic cavity, thin ribs and brachysternum. The BCRHS phenotype shows similarity to certain human short stature syndromes, in particular the human 3M syndrome-2. Here we report the identification of a likely disease-causing variant and propose an ovine model for human 3M syndrome-2. Results Eight positional candidate genes were identified among the 39 genes in the approximately 1 Mb interval to which the disease was mapped previously. Obscurin like cytoskeletal adaptor 1 (OBSL1) was selected as a strong positional candidate gene based on gene function and the resulting phenotypes observed in humans with mutations in this gene. Whole genome sequencing of an affected lamb (BCRHS3) identified a likely causal variant ENSOARG00000020239:g.220472248delC within OBSL1. Sanger sequencing of seven affected, six obligate carrier, two phenotypically unaffected animals from the original flock and one unrelated control animal validated the variant. A genotyping assay was developed to genotype 583 animals from the original flock, giving an estimated allele frequency of 5%. Conclusions The identification of a likely disease-causing variant resulting in a frameshift (p.(Val573Trpfs*119)) in the OBSL1 protein has enabled improved breeding management of the implicated flock. The opportunity for an ovine model for human 3M syndrome and ensuing therapeutic research is promising given the availability of carrier ram semen for BCRHS.
    Electronic ISSN: 1471-2156
    Topics: Biology
    Published by BioMed Central
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