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    A multipedigree linkage study of X-linked deafness: Linkage to Xq13-q21 and evidence for genetic heterogeneity
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    Abstract Two‐point linkage analyses yielded correct identification of linkage groups and good estimates of recombination frequencies in both males and females. Additional analyses compared various family structures for the total number of typed individuals necessary to detect linkage. Results suggest that for codominant markers with moderate recombination frequency, pedigrees may not provide substantial savings over nuclear families.
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    Human genetics
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    Replication
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    A large family with non-specific X-linked mental retardation (MRX) was first described in 1991 [Glass et al., 1991], with a suggestion of linkage 10 Xq26–27. The maximum lod score was 1.60 (θ = 0.10) with the F9 locus. The localisation of this MRX gene has now been established by linkage to microsatellite markers. Peak pairwise lod scores of 4.02 and 4.01 (θ = 0.00) were attained at the DXS1114 and DXS994 loci respectively. This MRX gene is now designated MRX27 and is localised to Xq24-26 by recombination events detected by DXS424 and DXS102. This regional localisation spans 26.2 cM on the genetic background map and defines another distinct MRX interval by linkage to a specific region of the X chromosome. © 1996 Wiley-Liss, Inc.
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    Evidence consistent with the existence of genetic linkage between bipolar disorder and three regions on chromosome 18, the pericentromeric region, 18q21, and 18q22-q23 have been reported. Some analyses indicated greater evidence for linkage in pedigrees in which paternal transmission of disease occurs. We have undertaken linkage analyses using 12 highly polymorphic markers spanning these three regions of interest in a sample of 48 U.K. bipolar pedigrees. The sample comprises predominantly nuclear families and includes 118 subjects with Diagnostic and Statistical Manual of Mental Disorders (DSM IV) bipolar I disorder and 147 subjects with broadly defined phenotype. Our data do not provide support for linkage using either parametric or nonparametric analyses. Evidence for linkage was not significantly increased by analyses that allowed for heterogeneity nor by analysing the subset of pedigrees consistent with paternal transmission. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:503–509, 1999. © 1999 Wiley-Liss, Inc.
    Pedigree chart
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    Evidence consistent with the existence of genetic linkage between bipolar disorder and three regions on chromosome 18, the pericentromeric region, 18q21, and 18q22-q23 have been reported. Some analyses indicated greater evidence for linkage in pedigrees in which paternal transmission of disease occurs. We have undertaken linkage analyses using 12 highly polymorphic markers spanning these three regions of interest in a sample of 48 U.K. bipolar pedigrees. The sample comprises predominantly nuclear families and includes 118 subjects with Diagnostic and Statistical Manual of Mental Disorders (DSM IV) bipolar I disorder and 147 subjects with broadly defined phenotype. Our data do not provide support for linkage using either parametric or nonparametric analyses. Evidence for linkage was not significantly increased by analyses that allowed for heterogeneity nor by analysing the subset of pedigrees consistent with paternal transmission. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:503–509, 1999. © 1999 Wiley-Liss, Inc.
    Pedigree chart
    Linkage (software)
    Genetic linkage
    Genome Scan
    Complete linkage
    Lod score
    • Numerous reports have been published concerning linkage of X-chromosome markers of the q28 region (including protan and deutan color blindness [CB] and glucose-6-phosphate dehydrogenase deficiency) to manic-depressive illness. We studied nine bipolar pedigrees (in which there was no male-tomale transmission) in an attempt to detect linkage, using three tightly linked polymorphic DNA loci, DXS15, DXS52 and F8C (factor 8 gene), all of which are closely linked to the CB and glucose 6-phosphate dehydrogenase classic Xq28 markers. Linkage to this region of Xq28 could be excluded unequivocally in these nine families. When these data were combined with our earlier series of bipolar pedigrees, informative for either protan or deutan CB, a total of 14 bipolar pedigrees have been studied, with no evidence of linkage or heterogeneity. At a recombination fraction (ø of 1%, this series had greater than 95% power to detect linkage if only 50% of the pedigrees studied were linked to the CB region. Our failure to confirm the previously reported linkage of manic-depressive illness to the CB region of the X chromosome indicates that this linkage is not as common as previously suggested.
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