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At least 19 recordsLinked to original sources
PubMed1979

Rough and fine linkage mapping of the Rhizobium meliloti chromosome.

A circular linkage map of the Rhizobium meliloti chromosome, obtained from R68.45-mediated crosses, has been revised by cotransductional analysis, after general transduction by DF2 phage. Three short chromosomal regions have been mapped by cotransduction. Comparison between conjugal and cotransductional data suggests that R68.45-mediated linkage measures are indeed rough. Cotransduction seems to be a useful tool for improving the linkage map of R. meliloti.

Chromosome Mapping↗
PubMed1979

Expanded linkage map of Vibrio cholerae.

An expanded linkage map of the Vibrio cholerae classical strain 162 chromosome has been prepared using a variety of new auxotrophic mutants. The chromosome consists of a single, linear linkage group. The map consists of 17 markers, which have been ordered; 20 mutational sites, which are tentatively ordered; five markers (ura-1, ser-2, mal-1, man-1, suc-1), which are linked but unordered; and three mutations (aro-2, cys-2 and cys-6) which showed little or no linkage. A proposal is made to standardize genetic nomenclature in V. cholerae genetic studies.

Chromosome Mapping↗
PubMed1977

Linkage mapping from pair-wise recombination data.

The problem of obtaining a genetic map of a linkage group from pair-wise recombination data is considered. A non-parametric approach is proposed, that does not require the definition of a mapping function, computation of coefficients of coincidence, nor knowledge of map length or sex differences in recombination. An application to Bridges and Morgan's (1923) data on chromosome 3 of Drosophila melanogaster is presented.

Chromosome Mapping↗
PubMed1978

Linkage map of Pseudomonas aeruginosa PAT.

The locations of new markers relative to markers previously mapped on the chromosome of Pseudomonas aeruginosa strain PAT were defined by generalized transduction with phage F116L and F1083. Although the marker orders of the various marker groups were deduced mainly from the results of two-factor crosses, the locations of a number of markers were confirmed by three-factor crosses. A linkage map of the chromosome of P. aeruginosa PAT was constructed which shows the relative locations of 50 genes. From the available data, the linkage maps of P. aeruginosa strains PAO and PAT appear to be similar.

Amino Acids↗
PubMed1975

Revision of the linkage map of Bacillus subtilis 168: indications for circularity of the chromosome.

A revision of the linkage map of the Bacillus subtilis 168 chromosome has been undertaken with the use of the generalized transducing phage PBS1. The mapping of four new markers (narB1, mtlB1, aroI906, and tre-12) has allowed a determination of the relative orientation of the purB-dal segment and its linkage with the lin markers. The chromosomal segment comprised between the sacQ36 and gtaA12 markers has been linked with the narA1, ctrA1, and sacA321 markers. The recA1 marker has been mapped relative to the thyA and citB17 markers. Indications of linkage have been found between the tre-12 and catA markers and the aroG932 and sacQ36 markers. According to these results, a circular genetic map of the chromosome of B. subtilis 168 is presented. Taken together, the transduction data and the order of marker replication determined by Harford in the accompanying paper support strongly the hypothesis of a symmetrical and fully bidirectional mode of replication for the B. subtilis 168 chromosome.

Bacillus subtilis↗
PubMed1976

Location of the Aspartase Gene (aspA) on the linkage map of Escherichia coli K12.

The aspartase (L-asparatate ammonia-lyase, EC. 4.3.I.I) structural gene, aspA, was mapped by two-factor and three-factor transductional crosses using phage PI. Cotransduction frequencies between aspA and other markers were: ampA (69%); frdA (48 TO 67%) mel (35%); purA (17%); fdp (I-6%). The sequence of markers within the corresponding segment (91 to 95 min) of the Escherichia coli linkage map was shown to be mel-aspA-ampA-frdA-purA-fdp.

Ammonia-Lyases↗
PubMed1979

Genetic circularity of the Proteus mirabilis linkage map.

The T incompatibility group plasmid R394 can mobilize the chromosome of Proteus mirabilis strain PM5006. It transferred relatively large segments, corresponding to at least 20 min on the D plasmid chromosomal map of the organism. The frequency of recombination for a large number of selected markers was nearly constant at 5 X 10(-6) per donor cell and it is concluded that mobilization takes place from a number of chromosomal sites. All recombinants were R+ and displayed all properties of the plasmid. By analysing crosses for co-inheritance frequencies of unselected markers, a number of chromosomal loci were assembled in linear array. Linkage between markers at the ends of this linkage group was established to markers at the respective termini of the existing D plasmid linkage group. This established a composite circular linkage map of genes of the P. mirabilis strain PM5006 chromosome.

Chromosome Mapping↗
PubMed1976

Temperature-sensitive mutants of herpes simplex virus type 2: a provisional linkage map based on recombination analysis.

Thirteen ts mutants of type 2 herpes simplex virus were backcrossed to a syncytial but not temperature-sensitive mutant of wild-type virus. This was an attempt to introduce a third marker, syncytial plaque morphology or syn, into at least some of the ts mutants. Three ts mutants carrying the syn marker were obtained but only one, ts 9, was satisfactory for genetic experiments. Three-factor crosses were carried out between ts 9 syn and the mutants which determined the order of eleven ts mutations relative to both the ts 9 mutation and the syn mutation. A provisional linkage map based both on the order derived from the three-factor crosses and on map distances from recombination frequencies has been prepared: it contains nine ts mutations and the syn mutation.

Cell Line↗
PubMed1978

DNA of Epstein-Barr virus. IV. Linkage map of restriction enzyme fragments of the B95-8 and W91 strains of Epstein-Barr Virus.

The arrangement of EcoRI, Hsu I, and Sal I restriction enzyme sites in the DNA of the B95-8 and W91 isolates of Epstein-Barr virus (EBV) has been determined from the size of the single-enzyme-cleaved fragments and from blot hybridizations that identify which fragments cut from the DNA with one enzyme contain nucleotide sequences in common with fragments cut from the DNA with a second enzyme. The DNA of the B95-8 isolate was the prototype for this study. The data indicate that (i) approximately 95 X 10(6) to 100 X 10(6) daltons of EBV (B95-8) DNA is in a consistent and unique sequence arrangement. (ii) Both termini are variable in length. One end of the molecule after Hsu I endonuclease cleavage consists of approximately 3,000 base pairs, with as many as 10 additional 500-base pair segments. The opposite end of the molecule after Sal I endonuclease cleavage consists of approximately 1,500 base pairs, with as many as 10 additional 500-base pair segments. (iii) The opposite ends of the molecule contain homologous sequences. The high degree of homology between the opposite ends of the molecule and the similarity in size of the "additional" 500-base pair segments suggests that there are identical repeating units at both ends of the DNA. The arrangement of restriction endonuclease fragments of the DNA of the W91 isolate of EBV is similar to that of the B95-8 isolate and differs from the latter in the presence of approximately 7 X 10(6) daltons of "extra" DNA at a single site. Thus, the size of almost all EcoRI, Hsu I, and Sal I fragments of EBV (W91) DNA is identical to that of fragments of EBV (B95-8) DNA. A single EcoRI fragment, C, of EBV (W91) DNA is approximately 7 X 10(6) daltons larger than the corresponding EcoRI fragment of EBV (B95-8) DNA. Digestion of EBV (W91) DNA with Hsu I or Sal I restriction endonucleases produces two fragments (Hsu I D1 and D2 or Sal I G2 and G3) which differ in total size by approximately 7 X 10(6) daltons from the fragments of EBV (B95-8) DNA. Furthermore, the EcoRI, Hsu I, and Sal I fragments of EBV (W91) and (B95-8) DNAs, which are of similar molecular weight, have homologous nucleotide sequences. Moreover, the W91 fragments contain only sequences from a single region of the B95-8 genome. Two lines of evidence indicate that the "extra" sequences present in W91 EcoRI fragment C are viral DNA and not cellular. (i) The molecular weight of the "enlarged" EcoRI C fragment of EBV (W91) DNA is identical to that of the EcoRI C fragment of another isolate of EBV (Jijoye), (ii) The HR-1 clone of Jijoye has previously been shown to contain DNA which is not present in the B95-8 strain but is present in the EcoRI C and Hsu I D2 and D1 fragments of EBV (W91) DNA (N. Raab-Traub, R. Pritchett, and E. Kieff, J. Virol. 27:388-398, 1978).

Cell Line↗
PubMed1977

Linkage map of the nitrogen fixation (nif) genes in Klebsiella pneumoniae.

The nif cistrons indentified by complementation analysis in the preceding paper (Dixon et al., 1977) were mapped with respect to hisD and to each other other by P1 cotransduction and three-factor reciprocal crosses. The order obrained was hisD nifB nifA (nifL) nifF nifE nifK nifD nifH. Analysis of hisD2-nif cotransduction data by the Wu equation (Wu, 1966) suggested that the nif genes are divided into two clusters: a his-proximal cluster comprising nifBA(L)F and a his-distal group of nifEKDH.

Chromosome Mapping↗
PubMed2005

Animal breeding and disease.

Single-locus disorders in domesticated animals were among the first Mendelian traits to be documented after the rediscovery of Mendelism, and to be included in early linkage maps. The use of linkage maps and (increasingly) comparative genomics has been central to the identification of the causative gene for single-locus disorders of considerable practical importance. The 'score-card' in domestic animals is now more than 100 disorders for which the molecular lesion has been identified and hence for which a DNA test is available. Because of the limited lifespan of any such test, a cost-effective and hence popular means of protecting the intellectual property inherent in a DNA test is not to publish the discovery. While understandable, this practice creates a disconcerting precedent. For multifactorial disorders that are scored on an all-or-none basis or into many classes, the effectiveness of control schemes could be greatly enhanced by selection on estimated breeding values for liability. Genetic variation for resistance to pathogens and parasites is ubiquitous. Selection for resistance can therefore be successful. Because of the technical and welfare challenges inherent in the requirement to expose animals to pathogens or parasites in order to be able to select for resistance, there is a very active search for DNA markers for resistance. The first practical fruits of this research were seen in 2002, with the launch of a national scrapie control programme in the UK.

Animal Diseases↗
PubMed1978

Mapping and characterization of the nad genes in Salmonella typhimurium LT-2.

An ampicillin enrichment technique was used to isolate 39 nicotinic acid-requiring mutants of Salmonella typhimurium LT-2. Using interrupted-mating and transductional mapping procedures, three loci, designated nadA, nadB, and nadC, were identified. These loci mapped at 33, 82, and 6 min, respectively, on the S. typhimurium linkage map. The arrangement of the loci on the Salmonella linkage map corresponded closely to the nadA, nadB, and nadC loci on the Escherichia coli K-12 linkage map, indicating that the de novo pathway to nicotinamide adenine dinucleotide and the genes governing the enzymes involved in this pathway in S. typhimurium are very similar to those in E. coli. Evidence is also presented which indicates that the product of the nadC locus in S. typhimurium LT-2 is the enzyme quinolinic acid phosphoribosyltransferase. All nadC mutants of S. typhimurium secreted between 2 and 8 mumol of quinolinic acid per 100 ml of secretion medium. In addition, none of the nadC mutants isolated were able to grow in 10(-3) M quinolinic acid, whereas all nadA and nadB mutants of S. typhimurium grew well in the presence of quinolinic acid. Transductional crosses between nadB mutants provided evidence suggestive of more than one locus in the nadB region.

Chromosome Mapping↗
PubMed1976

Genetic relatedness in the family Enterobacteriaceae.

Five criteria of genetic relatedness are considered. The first, transfer of plasmids between groups, is frequently not a good criterion, because transfer is possible between all genera of the Enterobacteriaceae and also to genera in other families. Though transfer to closely related groups is most frequent, host restriction and the properties of the plasmid may influence the transfer frequency as much as the relatedness of the donor and recipient. The second criterion is interspecies recombination (integration) of chromosomal genes transferred by Hfr strains. Crosses between closely related genera (E. coli and Shigella) gave high frequency of stable hybrids, but crosses between less related genera (E. coli and Salmonella) result in lower recombination, with the donor genes frequently integrated in nonallelic positions on the chromosome, or remaining as autonomous CCC-DNA. In crosses between distantly related genera such as E. coli and Proteus, all the donor DNA remained as CCC, with no detectable integration into the chromosome. Third, the linkage maps of different strains of a species such as E. coli or of closely related species are very similar. The linkage maps of E. coli and S. typhimurium are also similar, with one gene rearrangement, an inversion, distinguishing them. There are some indications of differences in gene order between E. coli and Yersinia and between E. coli and S. marcescens and considerable evidence for rearrangements in gene order between E. coli and P. mirabilis. No similarity between the linkage maps of E. coli and of nonenteric bacteria such as Pseudomonas was observed. Thus within the enteric bacteria there is striking similarity in order of genes between closely related genera, but major changes when less related genera, such as E. coli and P. mirabilis, are observed. are observed...

Bacterial Proteins↗
PubMed1979

Colinearity in the mouse genome: a study of chromosome 2.

The cytologic positions (determined by G-banding) of the breakpoints on mouse chromosome 2 of a series of ten reciprocal translocations were compared with their most probable genetic positions on the linkage map, as determined by studies on recombination with known chromosome 2 (= linkage group V) markers. The most probable proximaldistal orders of the genetic and cytologic breakpoints were found to be the same; i.e., the two sets of breakpoints were colinear. However, there was no close correspondence between these two measures of the distance apart of adjacent breakpoints, since some translocation breaks which were well separated in G-band positions seemed close together in terms of the linkage map, and vice versa. This helps to confirm LYON'S conclusion that in certain mouse chromosomes, including No. 2, the distribution of chiasmata is nonrandom.

Animals↗