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  • 1
    Electronic Resource
    Electronic Resource
    A source of variance in IQ unique to the lower-scoring monozygotic (MZ) cotwin (1986)
    Springer
    Behavior genetics 16 (1986), S. 509-516 
    Details
    ISSN: 1573-3297
    Keywords: twins ; heritability ; environment ; intelligence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Environmental factors more common in twins than singletons appear to be disadvantageous with respect to intelligence. If these factors contribute to within-pair differences in IQ, the effect should be found more in the cotwin lower in IQ (the low twin) than in the cotwin higher in IQ (the high twin). In this case, the variance of the low twins should exceed that of the high twins. This hypothesis was tested for five samples of monozygotic (MZ) twins and three samples of dizygotic (DZ) twins but was confirmed only for the MZ samples. These results suggest that there are disadvantageous environmental factors unique to MZ twins which contribute to within-pair variability. Such factors will cause heritability coefficients obtained using MZ twins to be underestimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066337
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins (1991)
    Springer
    Behavior genetics 21 (1991), S. 75-96 
    Details
    ISSN: 1573-3297
    Keywords: sexual orientation ; twins ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchial tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067668
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Increased heritability for lower IQ levels? (1991)
    Springer
    Behavior genetics 21 (1991), S. 397-404 
    Details
    ISSN: 1573-3297
    Keywords: twins ; heritability ; environment ; intelligence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Dettermanet al. (1990) presented evidence based on twins that the heritability of IQ may be higher in the lower part of the IQ range. We first offer an alternative test for differential heritability across the IQ range, based on the analysis of absolute intrapair differences of monozygotic versus dizygotic twins. We then review two previous studies, each containing more twins than the sample of Dettermanea al., which examined the distribution of intrapair absolute differences. In contrast to the study of Dettermanet al., both yielded results more compatible with higher heritability in the upper range of IQ. We discuss various interpretations of these findings and show how our proposed test might aid in distinguishing among them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065975
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Measurement Models for Sexual Orientation in a Community Twin Sample (2000)
    Springer
    Behavior genetics 30 (2000), S. 345-356 
    Details
    ISSN: 1573-3297
    Keywords: Homosexuality ; sexual orientation ; heritability ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Multivariate structural equation modeling techniques have been applied to examine the causes of individual differences in responses to several items concerning sexual orientation. To minimize potential ascertainment and response biases, the study sample involved a large (N = 4901) community-based cohort of Australian twins aged 18–52 who answered an anonymous questionnaire on sexual behavior and attitudes. The statistical power of the analysis was increased by the availability of multiple measures of sexual orientation (behaviors, attitudes and feelings), providing stronger evidence for the existence of additive genetic influences on this phenotype than in a previous analysis (Bailey et al., 2000). Estimates of the heritability of homosexuality in this sample ranged between 50 and 60% in females but were significantly lower (heritability of approximately 30%) in males.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026557719181
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Modeling the population dynamics of baculovirus-infected insect cells: Optimizing infection strategies for enhanced recombinant protein yields (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 432-441 
    Details
    ISSN: 0006-3592
    Keywords: nuclear polyhedrosis virus ; polyhedrin promoter ; population dynamics ; multiplicity of infection ; Poisson distribution ; baculovirus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The insect cell-baculovirus model presented here is capable of simulating cell population dynamics, extracellular virion densities, and heterologous product titers in reasonable agreement with experimental data for a wide rang of multiplicities of infection (MOI) and times of infection. The model accounts for the infection of a single cell by multiple virions and the consequences on the time course of infection. The probability of infection by more than one virion was approximated using the Poisson distribution, which proved to be a refinement over second-order kinetics. The model tracks initiation and duration of important events in the progression of infected cell development (virus replication, recombinant protein synthesis, and cell lysis) for subpopulations delineated by the time and extent of their initial infection. The model suggests infection strategies, weighing the importance of MOI and infection time. Maximum product titers result from infection in the early exponential growth phase with low MOI.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390409
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Production of a discrete, heterogeneous population of β-galactosidase polypeptides using baculovirus expression vectors (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 932-944 
    Details
    ISSN: 0006-3592
    Keywords: Spodoptera frugiperda ; Autographa californica ; nuclear polyhedrosis virus ; polyhedrin promoter ; β-galactosidase ; heterogeneous polypeptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gel electrophoresis analysis of immunoprecipitated β-galactosidase and polyhedrin-β-galactosidase expressed in Spodoptera frugiperda cells infected with recombinant Autograph californica nuclear polyhedrosis virus revealed the existence of a population of discrete β-galactosidase polypeptides. Several of the polypeptides observed in the fusion protein expression experiments exhibit a consistent pattern of slightly greater molecular weight when compared to the nonfusion β-galactosidase that is compatible with the hypothesis that these fusion protein fragments retain the N-terminal polyhedrin residues. Pulse-chase experiments showed that overall β-galactosidase degradation occurred at a negligible rate compared to the synthesis rate at 96 h postinfection, yet the fragments are observed for short pulse times. Degradation of several different β-galactosidase polypeptides was observed 24 h postinfection. Ribonucleic acid hybridization analysis of lacZ transcripts shows significant heterogeneity that may result from premature transcription termination. Although a proteolytic origin cannot be excluded, the data assembled suggest that premature termination of transcription or translation is the likely cause for the heterogeneous population of immunoreactive peptides observed. Many discrete forms of β-galactosidase polypeptides were also observed in studies with Escherichia coli, indicating that production of these heterogeneous forms is not a consequence of heterologous expression of the enzyme.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390908
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    Paper (German National Licenses)
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