Browsing by keyword "*Tandem Repeat Sequences"

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    • Dopamine D4 gene 7-repeat allele and attention deficit hyperactivity disorder
      Faraone, Stephen V.; Biederman, Joseph; Weiffenbach, Barbara; Keith, Tim; Chu, Monica P.; Weaver, Alix; Spencer, Thomas J.; Wilens, Timothy E.; Frazier, Jean A.; Cleves, Mario; et al. (1999-05-18)
      OBJECTIVE: Family, twin, and adoption studies show attention deficit hyperactivity disorder (ADHD) to have a substantial genetic component, and some studies have reported an association between ADHD and the dopamine D4 (DRD4) gene. METHOD: The authors recruited 27 triads that comprised an ADHD adult, his or her spouse, and their ADHD child. These triads were assessed for ADHD, and their DNA was genotyped for DRD4 alleles. RESULTS: A multiallelic transmission disequilibrium test suggested an association between ADHD and the DRD4 7-repeat allele. Among family members, the number of 7-repeat alleles predicted the diagnosis of ADHD. CONCLUSIONS: Prior reports of an association between ADHD and DRD4 generalize to families recruited through clinically referred ADHD adults. However, because there are some conflicting studies, further work is needed to clarify the role of DRD4 in the etiology of the disorder.

    • The mu switch region tandem repeats are important, but not required, for antibody class switch recombination
      Luby, Thomas M.; Schrader, Carol E.; Stavnezer, Janet; Selsing, Erik (2001-01-15)
      Class switch DNA recombinations change the constant (C) region of the antibody heavy (H) chain expressed by a B cell and thereby change the antibody effector function. Unusual tandemly repeated sequence elements located upstream of H chain gene exons have long been thought to be important in the targeting and/or mechanism of the switch recombination process. We have deleted the entire switch tandem repeat element (S(mu)) from the murine (mu) H chain gene. We find that the S(mu) tandem repeats are not required for class switching in the mouse immunoglobulin H-chain locus, although the efficiency of switching is clearly reduced. Our data demonstrate that sequences outside of the S(mu) tandem repeats must be capable of directing the class switch mechanism. The maintenance of the highly repeated S(mu) element during evolution appears to reflect selection for a highly efficient switching process rather than selection for a required sequence element.

    • The Smu tandem repeat region is critical for Ig isotype switching in the absence of Msh2
      Min, Irene M.; Schrader, Carol E.; Vardo, Joycelyn; Luby, Thomas M.; D'Avirro, Nicole; Stavnezer, Janet; Selsing, Erik (2003-10-01)
      Deficiencies of the Msh2 protein or the Smu tandem repeat (SmuTR) sequences each reduce isotype switching in mice by about 2- to 3-fold. We find that switching in mice deficient for both Msh2 and SmuTR is nearly ablated. We propose that the SmuTR provides closely spaced cleavage sites that can undergo switch recombination independent of Msh2, whereas cleavages in sequences flanking the SmuTR require Msh2 processing to allow recombinational joining. We also find that changes in Smu sequences alter the focus of switch junctions within Sgamma sequences, indicating that sequences of switch regions act together in the choice of switch recombination junctions. These findings help to explain the conservation of tandemly repeated switch regions associated with heavy chain constant genes in species capable of switching.