Organization of the a-Globin Genes in the Chinese a-Thalassemia Syndromes

group of inherited anemias, the clinical severity of which has been shown to increase with the number ofa-globin structural genes deleted. Employing restriction endonuclease gene mapping, we defined the organization of the a-globin genes in cellular DNA from Chinese subjects with various a-thalassemia syndromes. The four a-globin genes of normals are at two loci located on a 23.0-kilobase pair (kb) Eco RI fragment. In deletion type hemoglobin-H disease the 5 ' a-globin locus is deleted and the single 3 ' a-globin locus is found on a 19.0-kb Eco RI fragment. In a-thalassemia-2 there are two a-globin genes on a 23.0-kb Eco RI fragment and one on a 19.0-kb fragment. In a-thalassemia-I and the nondeletion type of hemoglobin-H disease the two a-globin genes are at two loci on one chromosome and none reside on the other chromosome

Rare Etiology of Autosomal Recessive Disease in a Child with Noncarrier Parents

A child with maple syrup urine disease type 2 (MSUD2) was found to be homozygous for a 10-bp MSUD2-gene deletion on chromosome 1. Both purported parents were tested, and neither carries the gene deletion. Polymorphic simple-sequence repeat analyses at 15 loci on chromosome 1 and at 16 loci on other chromosomes confirmed parentage and revealed that a de novo mutation prior to maternal meiosis I, followed by nondisjunction in maternal meiosis II, resulted in an oocyte with two copies of the de novo mutant allele. Fertilization by a sperm that did not carry a paternal chromosome 1 or subsequent mitotic loss of the paternal chromosome 1 resulted in the propositus inheriting two mutant MSUD2 alleles on two maternal number 1 chromosomes

Duchenne/Becker muscular dystrophy carrier detection using quantitative PCR and fluorescence-based strategies.

Dystrophin gene deletions account for up to 68% of all Duchenne (DMD) and Becker (BMD) muscular dystrophy mutations. In affected males, these deletions can be detected easily using multiplex PCR tests which monitor for exon presence. In addition, quantitative dosage screening can discriminate female carriers. We previously analyzed multiplex PCR products by gel electrophoresis and quantitation of fluorescently labeled primers with the Gene Scanner in order to test carrier status. These multiplex PCR protocols detect DMD gene deletions adequately, but require up to 18 pairs of fluorochrome-labeled primers. We previously described two alternative fluorescent labeling strategies, each with approximately 1,000-fold greater sensitivity than ethidium bromide staining, which can be used to quantify the products of multiplex PCR. The first method uses the DNA intercalating thiazole orange dye TOTO-1 to stain PCR products after 20 cycles. In the second method, fluorescein-12,2'-dUTP is incorporated into products during PCR as a fluorescent tag for subsequent quantitative dosage studies. Both methods label all multiplexed exons including the 506 bp exon 48 fragment that is difficult to detect and quantify by standard ethidium bromide staining. Using this approach, we determined DMD/BMD carrier status in 24 unrelated families using a fluorescent fragment analyzer. Analysis of fluorochrome-labeled PCR products facilitates quantitative multiplex PCR for gene-dosage analysis

Chromosomal localization of GABAA receptor subunit genes: relationship to human genetic disease

Hybridization of {GABAA} receptor probes to human chromosomes in situ and to {DNA} from sorted human chromosomes has localized the genes encoding a β subunit and three isoforms of the a subunit. The α2 and β genes are both located on chromosome 4 in bands p12–p13 and may be adjacent. The α1 gene is on chromosome 5 (bands q34–q35) and the α3 gene is on the X chromosome. The a3 locus was mapped also on the mouse X chromosome using genetic break-point analysis in an interspecies pedigree. The combined results locate the human a3 gene within band Xg28, in a location that makes it a candidate gene for the X-linked form of manic depression