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Mouse molecular cytogenetic resource: 157 BACs link the chromosomal and genetic maps.

We have established a collection of strong molecular cytogenetic markers that span the mouse autosomes and X chromosome at an average spacing of one per 19 Mb and identify 127 distinct band landmarks. In addition, this Mouse Molecular Cytogenetic Resource relates the ends of the genetic maps to their chromosomal locations. The resource consists of 157 bacterial artificial chromosome (BAC) clones, each of which identifies specific mouse chromosome bands or band borders, and 42 of which are linked to genetic markers that define the centromeric and telomeric ends of the Whitehead/MIT recombinational maps. In addition, 108 randomly selected and 6 STS-linked BACs have been assigned to single chromosome bands. We have also developed a high-resolution fluorescent reverse-banding technique for mouse chromosomes that allows simultaneous localization of probes by fluorescence in situ hybridization (FISH) with respect to the cytogenetic landmarks. This approach integrates studies of the entire mouse genome. Moreover, these reagents will simplify gene mapping and analyses of genomic fragments in fetal and adult mouse models. As shown with the MMU16 telomeric marker for the trisomy 16 mouse model of Down syndrome, these clones can obviate the need for metaphase analyses. The potential contribution of this resource and associated methods extends well beyond mapping and includes clues to understanding mouse chromosomes and their rearrangements in cancers and evolution. Finally it will facilitate the development of an integrated view of the mouse genome by providing anchor points from the genetic to the cytogenetic and functional maps of the mouse as we attempt to understand mutations, their biological consequences, and gene function.

Animals↗

Genetic mapping of GBE1 and its association with glycogen storage disease IV in American Quarter horses.

Comparative biochemical and histopathological data suggest that a deficiency in the glycogen branching enzyme (GBE) is responsible for a fatal neonatal disease in Quarter Horse foals that closely resembles human glycogen storage disease type IV (GSD IV). Identification of DNA markers closely linked to the equine GBE1 gene would assist us in determining whether a mutation in this gene leads to the GSD IV-like condition. FISH using BAC clones as probes assigned the equine GBE1 gene to a marker deficient region of ECA26q12-->q13. Four other genes, ROBO2, ROBO1, POU1F1, and HTR1F, that flank GBE1 within a 10-Mb segment of HSA3p12-->p11, were tightly linked to equine GBE1 when analyzed on the Texas A&M University 5000 rad equine radiation hybrid panel, while the GLB1, MITF, RYBP, and PROS1 genes that flank this 10-Mb interval were not linked with markers in the GBE1 group. A polymorphic microsatellite (GBEms1) in a GBE1 BAC clone was then identified and genetically mapped to ECA26 on the Animal Health Trust full-sibling equine reference family. All Quarter Horse foals affected with GSD IV were homozygous for an allele of GBEms1, as well as an allele of the most closely linked microsatellite marker, while a control horse population showed significant allelic variation with these markers. This data provides strong molecular genetic support for the candidacy of the GBE1 locus in equine GSD IV.

1,4-alpha-Glucan Branching Enzyme↗

Spontaneous transformation and its use for genetic mapping in Bacillus subtilis.

Using a simple semi-synthetic competence and sporulation medium (CSM), we found evidence that Bacillus subtilis cells transformed in the competence phase can sporulate, indicating that genetic information acquired during the competence phase is inherited by the next generation after germination of the transformed spores. Moreover, the results from mixed cell culture experiments suggest that spontaneous genetic transformation can occur between competent cells and DNA released from lysed cells in the natural environment. We also found evidence that the spontaneous transformation system can be used for genetic mapping in B. subtilis.

Bacillus subtilis↗

Phylogenetic distribution and genetic mapping of a (GGC)n microsatellite from rice (Oryza sativa L.).

DNA microsatellites are ubiquitously present in eukaryotic genomes and represent a vast source of highly informative markers. We describe in this article a (GGC)n microsatellite which is widely distributed in eukaryotic genomes. Using polymerase chain reaction (PCR) techniques and DNA sequencing, we demonstrated for the first time in plant species that a (GGC)n microsatellite locus is moderately polymorphic. Six alleles are present at this locus in rice and length polymorphisms are caused by variation in the number of tandem GGC repeats. By scoring a backcross mapping population, we were able to demonstrate that this locus is stably inherited and does not link to any known RFLP markers on the rice RFLP map. Our results suggest that DNA microsatellites should be useful in plants for construction of genetic linkage maps, extension of the existing genetic linkage maps, linkage analysis of disease and pest resistance genes, and the study of population genetics.

Base Sequence↗

[Construction of a genetic map of the chromosome of Vibrio cholerae based on conjugational crossings].

The results of cholera vibrio chromosomal mapping using Vibrio cholerae classica and V. cholerae eltor donor strains obtained with the help of various R. plasmids, are summarized in the paper. A genetic map of V. cholerae chromosome was established showing the order of 35 gene markers. The relationship between the genetic structures of cholera eltor and classical vibrio biotypes is discussed.

Chromosome Mapping↗

Genetic mapping of cancer susceptibility/resistance loci in the mouse.

Genetic linkage experiments using crosses between mouse inbred strains with an inherited predisposition and resistance to lung cancer make it possible to investigate the genetics of the complex inheritance of susceptibility and resistance to lung cancer. We have previously mapped a major locus (pulmonary adenoma susceptibility 1, Pas1) affecting inherited predisposition to lung cancer in mice onto chromosome 6, near Kras2. Appropriate crosses that include Pas1/+ mice provide a model system for identifying loci that can modify the lung cancer predisposition phenotype caused by Pas1. Using this approach, we mapped the pulmonary adenoma resistance 1 (Par1) locus on to mouse chromosome 11; this locus selectively inhibits lung tumor development in Pas1/+ animals and therefore behaves like a modulator gene of Pas1. More recently, we have mapped lung tumor modifier loci specifically affecting the initiation and progression of lung cancer. Thus experimental models provide an essential tool for the mapping of lung cancer susceptibility/resistance genes and for the subsequent cloning of candidate genes.

Adenoma↗

Genetic mapping of mitochondrial markers by recombinational analysis in Chlamydomonas reinhardtii.

The mitochondrial genome of Chlamydomonas reinhardtii is a 15.8 kb linear DNA molecule present in multiple copies. In crosses, the meiotic products only inherit the mitochondrial genome of the mating type minus (paternal) parent. In contrast mitotic zygotes transmit maternal and paternal mitochondrial DNA copies to their diploid progeny and recombinational events between molecules of both origins frequently occur. Six mitochondrial mutants unable to grow in the dark (dk- mutants) were crossed in various combinations and the percentages of wild-type dk+ recombinants were determined in mitotic zygotes when all progeny cells had become homoplasmic for the mitochondrial genome. In crosses between strains mutated in the COB (apocytochrome b) gene and strains mutated in the COX1 (subunit 1 of cytochrome oxidase) gene, the frequency of recombination was 13.7% (+/- 3.2%). The corresponding physical distance between the mutation sites was 4.3 kb. In crosses between strains carrying mutations separated by about 20 bp, a recombinational frequency of 0.04% (+/- 0.02%) was found. Two other mutants not yet characterized at the molecular level were also used for recombinational studies. From these data, a linear genetic map of the mitochondrial genome could be drawn. This map is consistent with the positions of the mutation sites on the mitochondrial DNA molecule and thereby validates the method used to generate the map. The frequency of recombination per physical distance unit (3.2% +/- 0.7% per kilobase) is compared with those obtained for other organellar genomes in yeasts and Chlamydomonas.

Animals↗

High-resolution genetic mapping of the leaf stripe resistance gene Rdg2a in barley.

The dominant gene Rdg2a of barley conferring resistance to the hemi-biotrophic seed-borne pathogen Pyrenophora graminea is located in the distal region of chromosome arm 1 (7H)S. As the first step towards isolating the gene, a high-resolution genetic map of the region was constructed using an F(2) population of 1,400 plants (Thibaut Rdg2axMirco). The map included six classes of resistance gene analogues (RGAs) tightly associated with Rdg2a. Rdg2a was delimited to a genetic interval of 0.14 cM between the RGAs ssCH4 and MWG851. Additional markers were generated using the sequence from the corresponding region on rice chromosome 6, allowing delimitation of the Rdg2a syntenic interval in rice to a 115 kbp stretch of sequence. Analysis of the rice sequence failed to reveal any genes with similarity to characterized resistance genes. Therefore, either the rice-barley synteny is disrupted in this region, or Rdg2a encodes a novel type of resistance protein.

Ascomycota↗

Localization of the FAR3 gene: genetic mapping and molecular cloning using a chromosome walk-'n'-roll strategy.

FAR3 is a newly-discovered yeast gene required specifically for pheromone-mediated cell cycle arrest. I have used strains harboring the far3-1 mutation to map the gene to the right arm of chromosome XIII, establishing the gene order CEN13-LYS7-MCM1-FAR3. I cloned the FAR3 gene based on its genetic map position using a strategy that combined chromosome walking and a related technique termed 'chromosome rolling'. In addition to the genetic and physical localization of FAR3, I present data that suggest corrections to the tentative map positions of VAN1 and ARG80.

Cell Cycle↗

GENETIC MAPPING OF VI AND SOMATIC ANTIGENIC DETERMINANTS IN SALMONELLA.

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Barbara Krauskopf, and L. S. Baron. Genetic mapping of Vi and somatic antigenic determinants in Salmonella. J. Bacteriol. 90:302-308. 1965.-The Vi antigen and somatic antigen 9 were transferred to Salmonella typhimurium recipients by mating with S. typhosa Hfr TD-7, and the genetic determinants of these antigens were located. A gene responsible for Vi antigen expression, ViB was found to be associated with the inlpurA-pyrB linkage group, and the order ViB-inl-purA-pyrB was established. The determinant of somatic antigen 9 was found closely linked to the his gene, and cotransduction of these determinants was accomplished with phage PLT-22. Moreover, all conjugation and transduction hybrids which received the somatic antigen 9 determinant concurrently lost somatic antigen 4. Similarly, S. typhosa hybrids produced by transfer of his and the gene for somatic antigen 4 from S. typhimurium Hfr B2, or by cotransduction of these genes with PLT-22, also lost somatic antigen 9. These results indicated that the genetic determinants of the somatic antigen 9 and 4 are probably allelic. A second Vi antigen determinant, ViA, located near his, was discovered in matings of S. typhimurium Hfr B2 with a Vi-negative S. typhosa recipient. Vi-positive S. typhosa hybrids were obtained from this cross in which neither parent expressed the Vi antigen, indicating that this Vi determinant of S. typhosa is present also in S. typhimurium.

Agglutination↗

Genetic mapping of variation in spatial learning in the mouse.

Inbred strains of mice are known to differ in their performance in the Morris water maze task, a test of spatial discrimination and place navigation in rodents, but the genetic basis of individual variation in spatial learning is unknown. We have mapped genetic effects that contribute to the difference between two strains, DBA/2 and C57BL6/J, using an F2 intercross and methods to detect quantitative trait loci (QTL). We found two QTL, one on chromosome 4 and one on chromosome 12, that influence behavior in the probe trial of the water maze (genome-wide significance p = 0.017 and 0.015, respectively). By including tests of avoidance conditioning and behavior in a novel environment, we show that the QTL on chromosomes 4 and 12 specifically influence variation in spatial learning. QTL that influence differences in fearful behavior (on chromosomes 1, 3, 7, 15, and 19) operate while mice are trained in the water maze apparatus.

Animals↗

Genomic organization and genetic mapping of the bovine PREF-1 gene.

As a potential regulator of nutrient partitioning in beef cattle, we have cloned and genetically mapped the bovine PREF-1 gene. A full-length PREF-1 cDNA was isolated by iterative purification from a mixed-tissue cDNA library to which adipose contributed mRNA. Analysis of partial cDNAs from this library revealed that the 3'-terminal exon of the bovine PREF-1 mRNA is spliced in a manner analogous to its murine ortholog. However, we have also detected a PREF-1 splice form apparently unique to cattle. Aside from this alternative selection of a splice donor in the bovine fifth exon, the exon/intron junctions of the bovine PREF-1 gene recapitulate those observed for mice. The sequences proximal to the bovine PREF-1 transcription start site are homologous to the mouse PREF-1 promoter. Importantly, the sequence experimentally identified as critical to PREF-1 "suppression in adipocyte differentiation" is conserved in the bovine gene. The bovine PREF-1 gene was mapped to the telomeric end of BTA 21 by virtue of a physically linked microsatellite with seven alleles and 285 informative meiosis.

Amino Acid Sequence↗

Genetic mapping in Xenopus laevis: eight linkage groups established.

Inheritance of alleles at 29 electrophoretically detected protein loci and one pigment locus (albinism) was analyzed in Xenopus laevis by backcrossing multiply heterozygous individuals generated by intersubspecies hybridization. Pairwise linkage tests revealed eight classical linkage groups. These groups have been provisionally numbered from 1 to 8 in an arbitrarily chosen order. Linkage group 1 includes ALB-2 (albumin), ADH-1 (alcohol dehydrogenase), NP (nucleoside phosphorylase), and ap (periodic albinism). Linkage group 2 contains ALB-1 and ADH-2, and probably is homeologous to group 1. Linkage group 3 comprises PEP-B (peptidase B), MPI-1 (mannosephosphate isomerase), SORD (sorbitol dehydrogenase), and mIDH-2 (mitochondrial isocitrate dehydrogenase). Linkage group 4 contains GPI-1 (glucosephosphate isomerase) and EST-4 (esterase 4). Linkage group 5 contains GPI-2 and PEP-D (peptidase D). Linkage group 6 comprises ACP-3 (acid phosphatase), sME (cytosolic malic enzyme), and GLO-2 (glyoxalase). Linkage group 7 consists of sSOD-1 (cytosolic superoxide dismutase), GPD-2 (glycerol-3-phosphate dehydrogenase), mME (mitochondrial malic enzyme), and the sex determining locus. Linkage group 8 includes FH (fumarate hydratase) and TRF (transferrin). Recombination frequencies between linked loci showed differences related to the genomic constitution (parental subspecies) and to the sex of the heterozygous parent. Independent assortment was observed between the duplicate ALB loci. This is true for the duplicate ADH, GLO, and MPI loci as well, supporting the view that these genes have been duplicated as part of a genome duplication that occurred in the evolutionary history of X. laevis. Comparative analysis of genetic maps reveals a possible conservation of several linkages from the Xenopus genome to the human genome.

Albinism↗

Genetic mapping in sugarcane, a high polyploid, using bi-parental progeny: identification of a gene controlling stalk colour and a new rust resistance gene.

Modern sugarcane cultivars (Saccharum spp) are highly polyploïd and aneuploid interspecific hybrids (2n = 100-130). Two genetic maps were constructed using a population of 198 progeny from a cross between R570, a modern cultivar, and MQ76-53, an old Australian clone derived from a cross between Trojan (a modern cultivar) and SES528 (a wild Saccharum spontaneum clone). A total of 1,666 polymorphic markers were produced using 37 AFLP primer combinations, 46 SSRs and 9 RFLP probes. Linkage analysis led to the construction of 86 cosegregation groups for R570 and 105 cosegregation groups for MQ76-53 encompassing 424 and 536 single dose markers, respectively. The cumulative length of the R570 map was 3,144 cM, while that of the MQ76-53 map was 4,329 cM. Here, we integrated mapping information obtained on R570 in this study with that derived from a previous map based on a selfed R570 population. Two new genes controlling Mendelian traits were localized on the MQ76-53 map: a gene controlling the red stalk colour was linked at 6.5 cM to an AFLP marker and a new brown rust resistance gene was linked at 23 cM to an AFLP marker. Besides another previously identified brown rust resistance gene (Bru1), these two genes are the only other major genes to be identified in sugarcane so far.

Basidiomycota↗

[Genetic mapping of the mitochondrial markers of antibiotic resistance in PG-strain Saccharomyces cerevisiae yeasts].

The mitochondrial mutations conferring resistance to antibiotics erythromycin, neomycin, oligomycin and mucidin, have been isolated in a number of strains. An attempt was made to genetically map these markers. The principle of coretention/or loss of two markers in UV induced petite mutants was used for localisation of the mitochondrial markers. The unique order of markers E-O-M-N was established in our experiments. The preferential loss of the Nr marker in petite mutants was observed. No significant differences in the gene order and in gene relative distances were observed between our PG strain and other nonrelated strains of Saccharomyces cerevisiae.

Anti-Bacterial Agents↗

A Bayesian approach for constructing genetic maps when markers are miscoded.

The advent of molecular markers has created opportunities for a better understanding of quantitative inheritance and for developing novel strategies for genetic improvement of agricultural species, using information on quantitative trait loci (QTL). A QTL analysis relies on accurate genetic marker maps. At present, most statistical methods used for map construction ignore the fact that molecular data may be read with error. Often, however, there is ambiguity about some marker genotypes. A Bayesian MCMC approach for inferences about a genetic marker map when random miscoding of genotypes occurs is presented, and simulated and real data sets are analyzed. The results suggest that unless there is strong reason to believe that genotypes are ascertained without error, the proposed approach provides more reliable inference on the genetic map.

Bayes Theorem↗