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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 399 (1999), S. 214-215 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Yu and Shepard have reported a preference for heavy women with high waist-to-hip ratios (WHR) in a culturally isolated population in southeast Peru. Their findings are interesting because a preference for low WHR is widespread in westernized populations. However, we disagree with their argument ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 389 (1997), S. 344-344 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The proportion of male to female births increases during and shortly after periods of war. We show that the age difference between parents (age of husband−age of wife) predicts the sex of the first child. We also find that in England and Wales, the mean spouse age difference increased ...
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 32 (1983), S. 289-292 
    ISSN: 1572-8358
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Under the influence of deleterious mutation and selection a population will reach equilibrium and contain individuals with [0, 1, 2 - - mutations.] This deterministic equilibrium distribution is exactly the same for asexual and sexual populations. The size of the optimal class (n o), i.e. the class with the smallest number of mutations, is determined by the genome mutation rate (U) and the average selective disadvantage (s) of the mutations. A large U and small s gives a very small n o. If n o is small in an asexual population it will be lost by drift and this causes a reduction in the mean fitness of the population (by the ratchet mechanism). It is argued that diploidy (when compared to haploidy) increases U and reduces s. Values of U and s observed from Drosophila indicate a diploid would have a vanishingly small n o. The argument suggests Muller's ratchet is more powerful than previously accepted in asexual species derived from diploid sexual ancestors.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 35 (1986), S. 149-162 
    ISSN: 1572-8358
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is evidence that asexual reproduction has a long-term disadvantage when compared to sexual reproduction. This disadvantage is usually assumed to arise from the more efficient incorporation of advantageous mutations by sexual populations. We consider here the effect on asexual and sexual populations of changes in the fitness of harmful mutations. It is shown that the re-establishment of equilibrium following environmental change is generally faster in sexual populations, and that the mutational load experienced by the sexual population can be significantly less during this period than that experienced by an asexual one. Changes in the fitness of harmful mutations may therefore impose a greater long-term disadvantage on asexual populations than those which are sexual.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 33 (1984), S. 219-225 
    ISSN: 1572-8358
    Keywords: Muller's ratchet and favourable mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Under the influence of recurrent deleterious mutation and selection, asexual and sexual populations reach a deterministic equilibrium with individuals carrying 0,1,2,. . . harmful mutations. When a favourable mutation (a→A) occurs in an asexual population it will usually occur in an individual who has one or more (k) deleterious mutations. Muller's ratchet then applies as A will thereafter never occur in an individual with less than k mutations. If the selective advantage of A is less than the selective disadvantage of k harmful mutations then A will not spread. If it is greater it may spread carrying k deleterious mutations to fixation. Sexual populations are not affected in this way. A will spread through the population experiencing genomes with 0,1,2,. . . deleterious mutations in accordance with the deterministic equilibrium.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 25 (1976), S. 111-129 
    ISSN: 1572-8358
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A model is proposed which implicates molecular recognition systems as the major controlling factors in life cycle expression. It is envisaged that such systems are important in immune functioning and catabolic, metabolic molecule recognition at both inter- and intea-cellular level. These recognition systems have the following characteristics: 1) Specific recognition molecules (recognisers), e.g. vertebrate antibodies, invertebrate agglutinins and plant agglutinins may recognise specific substances, e.g. antigens, catabolic and metabolic molecules. 2) The range of possible recognisable substances is very wide and variable. 3) The recognisers may themselves be recognised by other recognisers. 4) Recognisers are usually produced in large amounts only on presentation of the appropriate recognisable molecule. 5) The progressive introduction of new recognisable molecules increases the recogniser interaction, this interaction causing depression of some recogniser types (immune depression) and facilitation of other types among which may be recognisers specific for self components (e.g. auto-immunity). 6) Low juvenile viability is associated with a restricted range of available recognisers, high adult viability with increasing recogniser range and some auto-immunity/immune depression, senescence with a wide range of available recognisers and extensive auto-immunity/immune depression. Life cycle patterns and their control are discussed. It is suggested control mechanisms may include: 1) Dietary restriction and in some periods complete nutritional abstinence. 2) Specific recogniser depression, genes implicated here are the various antigens (species and polymorphic) found on cell surfaces, in the serum and in various body fluids of vertebrates, e.g. ABO, MNSs, P, Rh, Le and other blood groups, the ABO and Le secretor antigens and the HL-A antigens. In addition the immune response and mixed lymphocyte culture loci are implicated. Finally life cycle control is discussed with relation to sexual selection.
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 370 (1994), S. 185-186 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Fluctuating asymmetry (FA), ran-dom fluctuations from perfect bilateral symmetry, has been used to study en-vironmental deteriorationU2 and sexual selection3"7, but the relationship between FA and aspects of function in domesti-cated animals has been neglected. We show here that FA in ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 252 (1974), S. 512-512 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] OWEN, Owen and Chanter1 have invoked Y-linked meiotic drive to explain the high frequency occurrence of all-female broods in some populations of the African butterfly Acraea encedon. This mechanism does not account for the following observations2 of these populations: first, that they only occur in ...
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2011-09-19
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2020-07-09
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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