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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.
    Pedigree chart
    Linkage (software)
    Genetic linkage
    Nuclear family
    Lod score
    Identification
    Genetic Analysis
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    • We examined linkage between schizophrenia and five genetic markers on chromosome 5 in six pedigrees. Analyses were run considering the affected phenotype to be schizophrenia, schizophrenia plus a spectrum of related disorders, and these disorders plus any axis I diagnosis. None of the analyses were suggestive of linkage at any of the markers, either considering the pedigrees individually or in the aggregate. In our pedigrees, multipoint linkage analyses excluded much of the region that had supported linkage in an earlier study. These findings are consistent with other attempts to replicate the chromosome 5 linkage finding.
    Pedigree chart
    Linkage (software)
    Genetic linkage
    Complete linkage
    Abstract Model‐based linkage analysis is the analysis of the cosegregation of genetic loci in pedigrees. The most common form of linkage analysis uses pedigrees selected due to the presence of individuals affected by a disease that is assumed or known to have a major genetic component. Genetic markers are then examined to identify loci that appear to be cotransmitted with the predisposing disease locus.
    Pedigree chart
    Genetic linkage
    Linkage (software)
    Genetic Analysis
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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
    Lod score
    Complete linkage
    Five pedigrees (including an expanded version of a previously reported pedigree) exhibited typical autosomal dominant retinitis pigmentosa were analysed for linkage of RP to 29 genetic markers. No significant lod scores resulted. The largest lod score is +1.51 and suggests linkage between RP and Rh blood group at an estimated recombination fraction of 20% in males and 40% in females. Further studies are needed to confirm or refute this suggested linkage.
    Pedigree chart
    Recombination Fraction
    Genetic linkage
    Linkage (software)
    Lod score
    Citations (28)
    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
    A family history of disease is a strong risk factor for testicular germ cell tumour (TGCT). In order to identify the location of putative TGCT susceptibility gene(s) we conducted a linkage search in 237 pedigrees with two or more cases of TGCT. One hundred and seventy-nine pedigrees were evaluated genome-wide with an average inter-marker distance of 10 cM. An additional 58 pedigrees were used to more intensively investigate several genomic regions of interest. Genetic linkage analysis was performed with the ALLEGRO software using two model-based parametric analyses and a non-parametric analysis. Six genomic regions on chromosomes 2p23, 3p12, 3q26, 12p13-q21, 18q21-q23 and Xq27 showed heterogeneity LOD (HLOD) scores of greater than 1, with a maximum HLOD of 1.94 at 3q26. Genome-wide simulation studies indicate that the observed number of HLOD peaks greater than one does not differ significantly from that expected by chance. A TGCT locus at Xq27 has been previously reported. Of the 237 pedigrees examined in this study, 66 were previously unstudied at Xq27, no evidence for linkage to this region was observed in this new pedigree set. Overall, the results indicate that no single major locus can account for the majority of the familial aggregation of TGCT, and suggests that multiple susceptibility loci with weak effects contribute to the disease.
    Pedigree chart
    Genetic linkage
    Genome Scan
    Linkage (software)
    Citations (143)