Biomedical subjects
Publications and source records attributed to J Ott.
Under the assumption of two family types, one with linkage and one without linkage, the number of phase-known double-backcross families required to detect heterogeneity is investigated. The case of testing for heterogeneity with two offspring per family is shown to be formally equivalent to testing for inbreeding effects in a sample of unrelated individuals.
M13 RF IV DNA may be prepared in vitro to contain phosphorothioate-modified internucleotidic linkages in the (-)strand only. Certain restriction enzymes react with this modified DNA to hydrolyze the (+)strand exclusively when a phosphorothioate linkage occurs at the normal cleavage point in the (-)strand. The reaction of Pvu I with M13mp2 RF IV DNA containing dCMPS residues in the (-)strand is of this type, and is exploited to allow subsequent digestion with exonuclease III of a portion of the (+)strand opposite different mutagenic mismatched oligonucleotide primers. Two methods are described by which this approach has been used to produce mutations in M13mp2 phage DNA with high efficiency as a result of simple and rapid in vitro manipulations. Plaques containing mutant phage in a genetically-pure form are obtained at a frequency of 40-66%, allowing their characterisation directly by sequence analysis without prior screening and plaque purification. The wide applicability of this approach is discussed.
The resonances in the 31P-NMR spectrum of the dodecamer d(GACGATATCGTC) have been assigned by regiospecific labelling with oxygen-17. All 11 resonances are clearly resolved at 26 degrees C. Most noticeably, individual resonances of the dinucleoside phosphates d(CpG), d(TpC), d(GpA) and d(ApT) which occur more than once can clearly be distinguished. This indicates that the position of the phosphate group in the oligomer influences its 31P-NMR shift. This observation is in agreement with what has been found for the 31P-NMR spectra of d(CGCGAATTCGCG) [Ott, J. and Eckstein, F. (1985) Biochemistry 24] and d(GGAATTCC) [Connolly, B.A. and Eckstein, F. (1984) Biochemistry 23, 5523-5527]. In general, the chemical shift appears the more at higher field the more central the dinucleoside phosphate is located in the oligomer. Exceptions are the resonances of dinucleoside phosphates of the type 5'-PyPu-3' which appear at lower field than expected from this rule. A reasonable correlation between 31P-NMR chemical shifts and the sum function of the base plane roll angles derived from Calladine's rule [Calladine, C.R. (1982) J. Mol. Biol. 161, 343-352] exists.
In unrelated individuals, their phenotypes at two gene loci may appear correlated. The two major reasons for such a deviation from independence are linkage disequilibrium (allelic association) and an interaction between the phenotypes. In this paper, it is shown how the usual chi-square test for association of phenotypes can be partitioned into two components, one being due to allelic association and the other being due to other causes of phenotypic association. The test is demonstrated with an example.
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Multilocus linkage analysis is investigated from the viewpoint of the efficiency of recombination estimates under different strategies for detecting linkage and determining gene order within a linkage group. We consider the appropriateness of assuming no interference with data available in human genetic studies. Examples are given to show the significance of multilocus analysis in humans. A computer program package, LINKAGE, for multilocus linkage analysis is described.
The phosphite approach to oligodeoxynucleotide synthesis has been applied to the filter disc support. The method is exemplified here by the preparation of eight decadeoxynucleotides.
Studies on the segregation of the red blood cell determinant Xg in 12 families with X-linked inheritance of agammaglobulinemia (XLA) in 3-4 generations suggested linkage of Xg with XLA. One extensive pedigree of a Dutch family with XLA in eight generations was investigated for Xg and the quantitative polymorphism 12E7. LIPED analysis indicated linkage disproven up to 25cM distance within this pedigree. Taken together with data obtained from two other informative XLA pedigrees and with published data, the results indicate no close linkage between XLA and Xg: 12E7, the distance between XLA and Xg being more than 20cM.
The increasing number of DNA polymorphisms characterized in humans will soon allow the construction of fine genetic maps of human chromosomes. This advance calls for a reexamination of current methodologies for linkage analysis by the family method. We have investigated the relative efficiency of two-point and three-point linkage tests for the detection of linkage and the estimation of recombination in a variety of situations. This led us to develop the computer program LINKAGE to perform multilocus linkage analysis. The investigation also enables us to propose a method of location scores for the efficient detection of linkage between a disease locus, or a new genetic marker, and a linkage group previously established from a reference panel of families. The method is illustrated by an application to simulated pedigree data in a situation akin to Duchenne muscular dystrophy. These results show that considerable economy and efficiency can be brought to the mapping endeavor by resorting to appropriate strategies of detecting linkage and by constructing the human genetic map on a common reference panel of families.
Poly(2-methylthio-7-deazainosinic acid) [poly(ms2c7I)] was enzymatically synthesized by polymerization of 2-methylthio-7-deazainosine 5'-diphosphate with polynucleotide phosphorylase from Micrococcus luteus in high yield. The homopolymer shows much higher thermal stability than its parent polynucleotides poly(7-deazainosinic acid) [poly(c7I)] and poly(I). Its sigmoidal melting curve and pronounced hypochromicity imply a rigid, ordered structure. Poly(ms2c7I), like poly(2-methylthio-inosinic acid) [poly(ms2I)], does not form a complex with poly(C) because of the bulky 2-methylthio substituent. On the other hand, two poly(ms2c7I) strands form very rigid triple strands with poly(A). Different from poly(I) and poly(c7I) the homopolymer poly(ms2c7I) is very stable against cleavage by nuclease S1 and ribonuclease T2 as expected from its rigid secondary structure.
A genetic linkage study performed on a large family with autosomal dominant Charcot-Marie-Tooth neuropathy (HMSN type I) showed affected family members to have slow motor nerve conduction velocities, hypoactive tendon reflexes, and distal muscle weakness and atrophy. Results excluded close linkage of the neuropathy in this family to the Duffy blood group locus on chromosome 1. Previous studies in other families have shown positive linkage of HMSN type I to the Duffy locus. The present results provide support for the concept of genetic heterogeneity in HMSN type I. Comparison of this new family with the previous families showing linkage to Duffy reveals that the hereditary neuropathy not linked to the Duffy locus may have less severe slowing of motor nerve conduction velocities and less prominent onion bulb change evident on sural nerve biopsy.
Heterogeneity of the recombination fraction may or may not involve a mixture of two groups of elements. For the mixture situation (families with or without linkage between two gene loci), Morton's homogeneity test is compared with another test (Admixture test) with respect to significance level, power, parameter estimation and classification of families. The Admixture test is shown generally to have superior properties in this situation.
Previous reports have shown linkage of hereditary motor and sensory neuropathy, type I (HMSN I), a dominantly inherited hypertrophic neuropathy, to the locus for the Duffy blood group on the long arm of chromosome 1. Two kinships that were extensively studied and reported almost 20 years ago and used to show heterogeneity among kinships with peroneal muscular atrophy and to characterize HMSN I were investigated for linkage to various blood erythrocyte and lymphocyte (HLA) antigens. Strong evidence against linkage to the Duffy blood group locus was found for one kinship, whereas suggestive evidence for linkage was found for the other. These data imply that HMSN I is heterogeneous--that is, caused by different genetic mechanisms. The HMSN I that is not linked to the Duffy locus might be identified as HMSN IA, and the HMSN I that is linked to the Duffy locus might be designated as HMSN IB. HMSN IA was not linked to other blood types or HLA antigens. In addition, no evidence for linkage to blood types and HLA was found for spastic paraplegia with peroneal muscular atrophy and sensory loss (HMSN V).
Poly(adenylic acids) containing the antibiotic tubercidin (7-deazaadenosine) form double strands with poly(uridylic acid) by Watson-Crick base pairing. The stability of these complexes is enhanced by an increasing adenosine content of the polymers. Whereas poly(tubercidylic acid) can bind only one poly(U) chain, the copolymers of adenylic and tubercidylic acid bind a second strand of poly(U). The melting temperatures imply a triple strand formation in a similar geometry as found for poly(A).2poly(U). The diminished hypochromicity of those complexes suggests semi-Hoogsteen base pairs, caused by the lack of N-7 in the antibiotic. As found for poly(A).poly(U), the double-stranded poly(Tu).poly(U) is not hydrolyzed by nuclease S1. In contrast to the four regular homopolyribonucleotides the single-stranded poly(Tu) is cleaved very rapidly. This may be due to a great flexibility of the polynucleotide chain. Moreover TuMP does not inhibit the enzymic digestion. Both phenomena imply a mechanism for the antibiotic action of tubercidin on the polymer level.
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A linkage study was performed on three families with classic Charcot-Marie-Tooth (CMT) hereditary neuropathy with clinical manifestations of autosomal dominant inheritance, distal muscle weakness and atrophy, hyporeflexia, and slow motor nerve conduction velocities. Two families comprising 3 and 4 generations and a total of 23 affected persons were informative for the Duffy locus known to be on the long arm of chromosome 1. The maximum total lod score was 2.297 at recombination fraction theta = .1. The third family was informative for PGM1 (on the short arm of chromosome 1). There was no evidence for linkage of CMT to PGM1 in this third family, but only values of theta less than .03 could be excluded. There was no evidence for linkage of CMT to seven other informative markers in these families. We conclude that the gene controlling the occurrence of dominant CMT may be approximately 10 centimorgans from the Duffy locus on the long arm of chromosome 1. Additional studies are required to confirm these findings.
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