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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Alu repetitive sequences are frequently involved in homologous and non-homologous recombination events in the α-cluster. Possible mechanisms involved in Alu-mediated recombination events are strand exchange, promoted by DNA pairing between highly homologous Alu repeats, and subsequent strand invasion. Alternatively, Alu sequences might play a more active role in recombinogenic processes in the α-cluster. We describe a novel 33-kb α°-thalassaemia deletion ––DUTCH encompassing the α- and zeta-globin genes and pseudogenes in a kindred of Dutch-Caucasian origin. This deletion appears similar, although not identical, to the previously described ––MEDII deletion. Cloning and sequencing of both the ––DUTCH and ––MEDII deletion breakpoints clearly indicate that the mechanism leading to these α°-thalassaemia deletions involves misalignment between the highly homologous tandemly arranged Alu repeats at both parental sides, which are normally 33 kb apart. Comparison of breakpoint positions along the Alu consensus sequence indicate the involvement of a 26-bp core sequence in two out of five α°-thalassaemia deletions. This sequence has been identified by others as a possible hotspot of recombination. These findings favour the idea that Alu repeats stimulate recombination events not only by homologous pairing, but also by providing binding sites for recombinogenic proteins.
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  • 2
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By screening 27 hypercalcaemic and 21 normocalcaemic subjects in a large Dutch pedigree with familial benign hypercalcaemia (FBH; McK. No. 14598) (McKusick 1983) for more than 35 genetic markers, it was found that linkage of FBH can be excluded at about 25 centimorgans (cM) from GM, 20 cM from ABO, 15 cM from MNS and HLA, 10cM from JK and PI, and 5cM each from ACP1, AK1, ADA, GPT1, and PGP.
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In this article we describe the molecular characterization of 104 independent α-thalassemia patients identified by hematological analysis and family studies. During the study, another six chromosomes were identified with rearrangements of the α-cluster or point mutations in the α2-globin gene, not associated with α-thalassemia, in healthy relatives of the patients. The molecular defects were established by Southern blot analysis and, if no deletions could be identified, the α-globin genes were investigated by denaturing gradient gel electrophoresis and single strand conformation analysis for the presence of point mutations. Following this strategy, we were able to identify the molecular basis of 131 independent α-thalassemia chromosomes. In two individuals, the α-thalassemia determinant could not be demonstrated at the molecular level. We identified eight different deletion and five non-deletion α-thalassemias, three rearrangements in the α-cluster, two α-chain variants, and a silent mutation in the α2-globin gene not associated with α-thalassemia. The large heterogeneity of α-thalassemia mutations seen in the Dutch population might be typical for nothern European countries where, besides the more common mutations introduced by migration, a variety of sporadic mutations was also found in the autochthonous population. The screening strategy as described here, capable of identifying a wide spectrum of both deletions and point mutations, identified 98% of the α-thalassemia determinants present in 133 chromosomes.
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We describe a novel mutation in the δ globin gene of a compound heterozygote for δ° thalassemia and a deletion type Gγ+(Aγδβ)° thalassemia. The δ gene was amplified using the polymerase chain reaction (PCR), and the amplified material was used in a direct sequencing experiment. The nucleotide sequence of the mutant δ gene showed that the insertion of an extra nucleotide at the third position of codon 91 in the second exon, which gives rise to a premature stop codon at position 94, leads to the silencing of this gene. The presence of the mutation in the carriers of δ-thalassemia in this family was confirmed by dot blot hybridization. A possible model for the insertion of the extra nucleotide is discussed.
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A detailed marker gene study in a large Dutch kindred segregating for a reciprocal translocation between the chromosomes 6 and 20, t(6;20) (p21;p13), revealed a close linkage between the HLA genes and the breakpoint on the short arm of 6. During this study an apparent peak lod score of 2.9 was obtained at a recombination value of 0.05 for a linkage between HLA and the breakpoint, indicating that the chromosomal region, carrying the HLA genes, is situated near the breakpoint in band 6p21 close to the transition to 6p22.
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  • 6
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The protein and gene structure of the Hp Johnson variant (Hp3) were analyzed in two related heterozygous individuals. The molecular weight (23kd) and amino acid composition of Hp3 alpha chain were in agreement with the triplicated structure first suggested by Smithies in 1964. Direct gene analysis by Southern blotting showed a three-fold tandem repeat of the same 1.7 kb DNA segment implicated in the Hp2 gene duplication. On the basis of these data a nine exon model for the Hp3 gene is proposed.
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  • 7
    ISSN: 1573-4927
    Keywords: Drosophila ; molybdoenzymes ; sulfite oxidase ; tungstate feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Sulfite oxidase (sulfite: ferricytochrome c oxidoreductase; EC 1.8.2.1) has been detected in Drosophila melanogaster and some of its properties have been studied. In most respects this enzyme resembles the mammalian sulfite oxidases except for its molecular weight (148,000), which is somewhat higher than that of rat sulfite oxidase (116,000). Cytochrome c, potassium-ferricyanide, and oxygen can serve as electron acceptors in the oxidation of sulfite by the enzyme. Although definite evidence can be obtained only through the analysis of the pure enzyme, experiments involving tungstate feeding suggest that Drosophila sulfite oxidase is most probably a molybdoenzyme. Extracts of mal flies show normal levels of sulfite oxidase, whereas lxd flies have only 5–10% of the activity of wild type, and in cin flies the enzyme is apparently absent. While it is possible that the lxd and cin mutations are at some level responsible for the defective synthesis of a molybdenum-containing cofactor (supposed to be present in most molybdoenzymes), the evidence accumulated so far by several authors and the results of the present investigation argue against the involvement of a Mo cofactor in the multiple enzyme deficiencies observed in mal flies.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 196 (1984), S. 141-145 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied the rDNA spacer length polymorphism in a sample of 121 individuals belonging to families of 2–3 generations. Our data, obtained by restriction pattern analysis of genomic DNA, confirmed the limited and discrete nature of this polymorphism. Using the pattern as a genetic marker, we analyzed the segregation of length variants in the different families and we investigated the possible occurrence of unequal crossing-over events among homologous and nonhomologous rDNA clusters. No direct evidence of recombination in the spacer region that we analyzed emeged from our study. All the differences in the restriction patterns observed among individuals from the same family could be explained as resulting from meiotic segregation. Family data showed a multichromosomal distribution of NTS length variants and demonstrated a direct correspondence between the frequency of a variant in the population and its degree of spreading on the different rDNA clusters.
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  • 9
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The human α-globin gene cluster (30 kb) is embedded in a GC-rich isochore very close to the telomere of Chromosome (Chr) 16p. The α-Locus Controlling Region (α-LCR) is located upstream of the adult α-globin genes and has been shown to be essential for their expression. In this study we have been looking for expressed genes in the region upstream of the α-globin cluster to understand the role of the LCR-like element in the expression and replication timing of flanking gene clusters. We show that the upstream α-globin region is conserved over a 75-kb range and includes at least two oppositely transcribed non-globin genes, here referred to as Mid1 and Dist1. Complementary DNA sequences of 250 bp and 2.5 kb from Mid1 (coordinate-68) and Dist1 (coordinate-90 to-99), respectively, were isolated from human and mouse. The deduced partial amino acid sequences of these cDNAs are 81% and 95% identical for the Mid1 and Dist1 gene respectively. We have cloned a mouse cosmid “contig” which includes Dist1, Mid1, and the entire murine α-globin cluster. The murine homolog of the α-LCR was mapped upstream of the mouse globin genes at approximately the same position as in the human locus. Our results indicate that, in mouse and human, the α-globin loci and their flanking sequences are homologous over a range of at least 130 kb. The structural homology of this region in both mammals suggests also a functional one and indicates the mouse as a potential model for studying the role of the α-LCR controlling element in the regulation of expression and replication timing of the flanking gene clusters.
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibacterial properties of the secretion from the female reproductive accessory glands of medfly Ceratitis capitata are mostly ascribed to the presence of two peptides, ceratotoxin A and B, which exhibit a strong activity against gram-positive and gram-negative bacterial strains, and show sequence and function homology with cecropins, melittin, and magainins.CD experiments performed in different solvents indicate the presence of a significant content of helical structures in organic solvent.Two-dimensional nmr results for ceratotoxin A in methanol show a helical behavior for the 8-25 region of the peptide. A Ramachandran classification of each residue for the structures obtained from distance geometry calculations lead to the definition of four structural families in which the central segment 10-19 is always helical and differences refer to residues 8-9 and 19-23.A sequence analysis of the two ceratotoxins and a systematic search on the protein data bank revealed the occurrence of a KX-hydrophobic-hydrophobic-P motif that seems to be important for helix stabilization. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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