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N Dahl

Publications and source records attributed to N Dahl.

At least 109 records · Page 6Linked to original sources
PubMed1991

Genetic mapping of loci for X-linked retinitis pigmentosa.

Linkage analysis was performed in three Swedish families segregating for X-linked retinitis pigmentosa (XLRP), using five polymorphic DNA markers assigned to Xp. Individual recombination events were analyzed and two- and five-point linkage analysis was undertaken. In one family, a XLRP locus was mapped to the same position as OTC corresponding to RP3. In two families, a disease locus linked to OTC was excluded. In one family, recombination events indicate a locus for XLRP outside the interval (DXS84-OTC-DXS255-DXS14), most likely on the centromeric side of DXS14.

Chromosome Mapping↗
PubMed1991

Genetic mapping of new DNA probes at Xq27 defines a strategy for DNA studies in the fragile X syndrome.

The fragile X syndrome is the most common cause of familial mental retardation and is characterized by a fragile site at the end of the long arm of the X chromosome. The unusual genetics and cytogenetics of this X-linked condition make genetic counseling difficult. DNA studies were of limited value in genetic counseling, because the nearest polymorphic DNA loci had recombination fractions of 12% or more with the fragile X mutation, FRAXA. Five polymorphic loci have recently been described in this region of the X chromosome. The positions of these loci in relation to FRAXA were defined in a genetic linkage study of 112 affected families. The five loci--DXS369, DXS297, DXS296, IDS, and DXS304--had recombination fractions of 4% or less with FRAXA. The closest locus, DXS296, was distal to FRAXA and had a recombination fraction of 2%. The polymorphisms at these loci can be detected in DNA enzymatically digested with a limited number of restriction endonucleases. A strategy for DNA studies which is based on three restriction endonucleases and on five probes will detect one or more of these polymorphisms in 94% of women. This strategy greatly increases the utility of DNA studies in providing genetic advice to families with the fragile X syndrome.

Chromosome Mapping↗
PubMed1990

Benign ovarian teratomas. An analysis of their cellular origin.

To determine the cellular origin of benign ovarian teratomas with a 46,XX chromosome constitution, DNA markers recognizing restriction fragment length polymorphisms (RFLPs) were hybridized to DNA from six teratomas and their hosts. DNA markers heterozygous in the host were completely heterozygous in two of the teratomas. The remaining four showed a mixture of homozygosity and heterozygosity. These results suggests that most of the analyzed benign ovarian teratomas arose from germ cells after the first meiotic division by failure of meiosis II. Teratomas heterozygous for all tested markers may arise from failure of meiosis I. In addition, 21 cases were karyotyped and analyzed for centromeric chromosome markers to study the mechanism by which they were generated. Three of these tumors were homozygous when the host was heterozygous and therefore resulted from a failure of meiosis II or duplication of a mature ovum. Three cases were heterozygous for the centromeric chromosomal marker like the host and therefore probably originate from a premeiotic cell or a cell in which meiosis I has failed. One ovarian teratoma had an aberrant karyotype 47,XX,+8.

Alleles↗
PubMed1990

Mapping of the gene for X-linked amelogenesis imperfecta by linkage analysis.

X-linked Amelogenesis imperfecta (AI) is a genetic disorder affecting the formation of enamel. In the present study two families, one with X-linked dominant and one with X-linked recessive AI, were studied by linkage analysis. Eleven cloned RFLP markers of known regional location were used. Evidence was obtained for linkage between the AI locus and the marker p782, defining the locus DXS85 at Xp22, by using two-point analysis. No recombination was scored between these two loci in 15 informative meioses, and a peak lod score (Zmax) of 4.45 was calculated at zero recombination fraction. Recombination was observed between the more distal locus DXS89 and AI, giving a peak lod score of 3.41 at a recombination fraction of .09. Recombination was also observed between the AI locus and the more proximal loci DXS43 and DXS41 (Zmax = 0.09 at theta max = 0.31 and Zmax = 0.61 at theta max = 0.28, respectively). Absence of linkage was observed between the AI locus and seven other loci, located proximal to DXS41 or on the long arm of the X chromosome. On the basis of two-point linkage analysis and analysis of crossover events, we propose the following order of loci at Xp22: DXS89-(AI, DXS85)-DXS43-DXS41-Xcen.

Amelogenesis Imperfecta↗
PubMed1990

Gaucher disease type III (Norrbottnian type) is caused by a single mutation in exon 10 of the glucocerebrosidase gene.

Three major forms (types I-III) of Gaucher disease (GD) have been identified. The largest group of patients with type III GD has been reported from the province of Norrbotten in Sweden. In the present study the genomes from two GD patients of Norrbottnian origin were examined for abnormalities in the glucocerebrosidase gene. In both individuals, a single nucleotide substitution was found in exon 10. This mutation, which results in the substitution of proline for leucine, is identical to the NciI mutation described by Tsuji and co-workers in GD patients of other ethnic origins. Nine additional patients with Norrbottnian GD were shown to be homozygous for the same mutation by restriction-enzyme digestion of DNA amplified by PCR.

Base Sequence↗
PubMed1989

Isolation of a DNA probe of potential use for diagnosis of the fragile-X syndrome.

A new cloned DNA probe (U6.2), which recognizes polymorphisms near the locus for the fragile-X syndrome, was isolated. No recombinations were observed between the probe and the disease locus, although recombinations were observed with several other probes known to be located close to the fragile site. The locus defined by the probe, DXS304, cosegregated with the fragile-X phenotype in 29 informative meioses (zeta = 4.97, tau = 0.00). The degree of polymorphism at this locus and its proximity to the fragile-X locus makes it useful for carrier diagnosis and as a new starting point for attempts to clone the gene responsible for the disease.

DNA Probes↗
PubMed1989

The polymorphic marker DXS304 is within 5 centimorgans of the fragile X locus.

The fragile X syndrome, which is the most common cause of inherited mental retardation, poses important diagnostic problems for genetic counseling. The development of diagnostic strategies based on DNA analysis has been impaired by the lack of polymorphic markers very close to the disease locus. Here we report that the polymorphic probe U6.2 (locus DXS304) is much closer to the fragile X locus than all the previously reported markers. A recombination fraction of 0.02 between DXS304 and the fragile X locus was estimated by multipoint linkage analysis (confidence interval 0.002 to 0.05). Our data suggest that DXS304 is distal to the fragile X locus. This marker thus represents a major improvement for carrier detection and prenatal diagnosis in fragile X families.

Chromosome Mapping↗
PubMed1989

Molecular Xp deletion in a male: suggestion of a locus for hypogonadotropic hypogonadism distal to the glycerol kinase and adrenal hypoplasia loci.

We have analyzed one patient with a syndrome of glycerol kinase deficiency (GKD), adrenal hypoplasia (AH), mental retardation (MR) and hypogonadotropic hypogonadism (HH). Although a cytogenetic analysis of the patient failed to reveal any detectable chromosomal abnormality, Southern blot analysis, using DNA probes from the Xp21-Xp22 region, revealed a molecular deletion localized between the DXS41 and the DXS268 loci. Our results together with those of others (van Ommen et al. 1986, 1987, Francke et al. 1987, Yates et al. 1987, Chelly et al. 1988) suggest that the GK gene is located between the DXS68 and DXS268 loci. In addition, we propose a locus for HH in Xp, distal to the genes for GK and AH.

Adrenal Insufficiency↗
PubMed1989

Linkage analysis of families with fragile-X mental retardation, using a novel RFLP marker (DXS 304).

A new polymorphic DNA marker U6.2, defining the locus DXS304, was recently isolated and mapped to the Xq27 region of the X chromosome. In the previous communication we describe a linkage study encompassing 16 fragile-X families and using U6.2 and five previously described polymorphic markers at Xq26-q28. One recombination event was observed between DXS304 and the fragile-X locus in 36 informative meioses. Combined with information from other reports, our results suggest the following order of the examined loci on Xq: cen-F9-DXS105-DXS98-FRAXA-DXS304-(DXS52-F8 -DXS15). The locus DXS304 is closely linked to FRAXA, giving a peak lod score of 5.86 at a corresponding recombination fraction of .00. On the basis of the present results, it is apparent that U6.2 is a useful probe for carrier and prenatal diagnosis in fragile-X families.

Chromosome Mapping↗
PubMed1988

Use of linked DNA probes for carrier detection and diagnosis of X-linked juvenile retinoschisis.

Diagnosis of X-linked juvenile retinoschisis (RS) was made in two nonrelated Swedish individuals with restriction fragment length polymorphisms, using probes that flank the RS locus. The X chromosome of a 1-year-old male infant, at risk, displayed the same haplotype as an affected brother for restriction fragment length polymorphisms, representing five linked markers, which extended between the DXS164 and the DXS85 loci and encompassed the RS locus. The diagnosis was confirmed by a clinical examination and an electroretinogram. The X chromosomes of a pregnant woman, an offspring of a carrier female, showed a different haplotype to that of her affected brother, at three linked loci that flanked the RS gene. She was excluded as a carrier with a high probability; hence, the fetus was unlikely to inherit an abnormal gene for this X-linked trait. In informed families a DNA-based diagnosis can serve as a valuable complement to an electroretinogram and a clinical examination in the diagnosis of RS, since these carrier females cannot currently be identified by other means.

Chromosome Mapping↗
PubMed1988

DNA linkage analysis of X-linked retinoschisis.

Four families with juvenile retionoschisis (RS) have been studied by linkage analysis utilizing eleven polymorphic X-chromosomal markers. The results suggest a close linkage between DXS43, DXS41, and DXS208 and the RS locus at Xp22. The RS locus is distal to the OTC locus, DXS84, and the DMD locus but proximal to DXS85. No recombination events were observed between the RS locus and DXS43 and DXS41. The maximum likelihood estimate of the recombination fraction (theta) was thus zero and the peak lod scores (z) were 4.98 (DXS43) and 4.09 (DXS41). The linkage data suggest that the gene order on Xp is DXS85-(DXS43, RS, DXS41)-DMD-DXS84-OTC.

Chromosome Mapping↗
PubMed1988

Tight linkage between type III Gaucher's disease (Norrbottnian type) and a MspI polymorphism within the gene for human glucocerebrosidase.

A MspI polymorphism was detected in the beta-glucocerebrosidase gene in 10 Swedish families affected by type III Gaucher's disease. The sizes of the polymorphic fragments were 1.70 and 1.75 kb and the disease was found to segregate with the 1.70-kb fragment in 32 meioses. Only the 1.75-kb fragment was detected in families with no history of Gaucher's disease. The results indicate that the mutation causing type III Gaucher's disease has occurred once within the Swedish population. The polymorphism is useful for carrier detection since biochemical tests sometimes give inconclusive results.

Deoxyribonuclease HpaII↗
PubMed1988

A case of complete trisomy 2p/triploidy mosaicism.

This report describes a newborn male infant with complete trisomy 2p in 80% and triploidy in 20% of cultured cells from peripheral blood. The boy was delivered by Caesarean section after 32 weeks of gestation because of signs of intrauterine asphyxia. The infant, who was utterly small for his gestational age, showed an aberrant motoric pattern and a high forehead, low-set ears, a prominent occiput and scoliosis, an extension defect in the knee joints and flexed, ulnar-deviated wrists. He had flexed thumbs, sandal gap bilaterally and syndactyly between toes III and IV bilaterally. Autopsy revealed multiple internal malformations.

Abnormalities, Multiple↗