The human orosomucoid (ORM) is controlled by two closely linked loci, ORM1 and ORM2, and two tandem genes, AGP1 and AGP2, encoding the proteins produced by the two loci, have been cloned. In this study the molecular basis of ORM1 polymorphism was investigated. For the detection of mutations the products of the six exons of each gene, amplified by the polymerase chain reaction (PCR), were screened by single-strand conformation polymorphism analysis. Subsequently, the exons with an altered migration pattern were gene-specifically amplified by nested PCR. Sequencing of the gene-specific PCR products showed that the three common ORM1 alleles result from A-->G transitions at the codons for amino acid positions 20 in exon 1 and 156 in exon 5 of the AGP1 gene: ORM1*F1 was characterized by CAG (Gln) and GTG (Val), ORM1*F2, by CAG (Gln) and ATG (Met), and ORM1*S, by CGG (Arg) and GTG (Val). The phylogenesis of the genes encoding these three ORM1 alleles is discussed.
SummaryViroid infection is associated with the production of short interfering RNAs (siRNAs), a hallmark of posttranscriptional gene silencing (PTGS). However, viroid RNAs autonomously replicating in the nucleus have not been shown to trigger the degradation of homologous RNA in the cytoplasm. To investigate the potential of viroids for the induction of gene silencing, non-infectious fragments of potato spindle tuber viroid (PSTVd) cDNA were transcriptionally fused to the 3 H end of the green¯uorescent protein (GFP)-coding region. Introduction of such constructs into tobacco plants resulted in stable transgene expression. Upon PSTVd infection, transgene expression was suppressed and partial de novo methylation of the transgene was observed. PSTVd-speci®c siRNA was detected but none was found corresponding to the gfp gene. Methylation was restricted almost entirely to the PSTVd-speci®c part of the transgene. Neither a gfp transgene construct lacking viroid-speci®c elements was silenced nor was de novo methylation detected, when it was introduced into the genetic background of the PSTVd-infected plant lines containing silenced GFP:PSTVd transgenes. The absence of gfp-speci®c siRNAs and of signi®cant methylation within the gfp-coding region demonstrated that neither silencing nor DNA methylation spread from the initiator region into adjacent 5 H regions.
A new genetic polymorphism of a human serum glycoprotein, the inter-alpha-trypsin-inhibitor (ITI), has been demonstrated by population and family studies. Sera were examined after neuraminidase treatment by isoelectric focusing on agarose gels followed by immunoblotting or by immunofixation with specific ITI-antiserum. Using this method, three common ITI phenotypes 1, 1-2 and 2, as well as two further rare ITI types 1-3 and 2-3 were disclosed. Genetically, these phenotypes are controlled by three allelic genes that determine a total of six phenotypes. These alleles are designated ITI*1, ITI*2 and ITI*3. The homozygous form of the third allele ITI*3 has not been found, as yet. The frequencies of ITI were examined in two population samples from Southern Germany (n = 248) and from Tyrol, Austria (n = 124). The gene frequencies of the common alleles ITI*1 and ITI*2 were 0.575 and 0.417, respectively, in Southern Germany, and 0.577 and 0.423, respectively, in Tyrol, Austria. The third allele ITI*3 was found only in the sample from Southern Germany, thus far, and was calculated to be 0.008.
Genotypes of the ABO blood group system were studied by PCR-RFLP analysis of the eight polymorphic nucleotide positions (nps) 261, 467, 526, 646, 703, 796, 802 and 803 of the cDNA from A transferase. In 169 unrelated German individuals, 17 genotypes were found and the calculated allele frequencies of A(Pro), A(Leu), B, O(T), O(A) and O2 were 0.2130, 0.0770, 0.0473, 0.4260, 0.2160 and 0.0207, respectively. These frequency data may provide useful additional information for disputed paternity and stain testing. A variant O allele, O2, was fout at a polymorphic frequency. As the nucleotide (np 261) of the O2 allele is the same as that of A and B alleles, the analysis of at least three nucleotide positions, i.e. nps 261, 526 and 802, is necessary to avoid mistyping of the ABO genotype.
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