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Genetic linkage maps of the red flour beetle, Tribolium castaneum, based on bacterial artificial chromosomes and expressed sequence tags.

A genetic linkage map was constructed in a backcross family of the red flour beetle, Tribolium castaneum, based largely on sequences from bacterial artificial chromosome (BAC) ends and untranslated regions from random cDNA's. In most cases, dimorphisms were detected using heteroduplex or single-strand conformational polymorphism analysis after specific PCR amplification. The map incorporates a total of 424 markers, including 190 BACs and 165 cDNA's, as well as 69 genes, transposon insertion sites, sequence-tagged sites, microsatellites, and amplified fragment-length polymorphisms. Mapped loci are distributed along 571 cM, spanning all 10 linkage groups at an average marker separation of 1.3 cM. This genetic map provides a framework for positional cloning and a scaffold for integration of the emerging physical map and genome sequence assembly. The map and corresponding sequences can be accessed through BeetleBase (http://www.bioinformatics.ksu.edu/BeetleBase/).

Animals↗

A high-density microsatellite consensus map for bread wheat (Triticum aestivum L.).

A microsatellite consensus map was constructed by joining four independent genetic maps of bread wheat. Three of the maps were F(1)-derived, doubled-haploid line populations and the fourth population was 'Synthetic' x 'Opata', an F(6)-derived, recombinant-inbred line population. Microsatellite markers from different research groups including the Wheat Microsatellite Consortium, GWM, GDM, CFA, CFD, and BARC were used in the mapping. A sufficient number of common loci between genetic maps, ranging from 52 to 232 loci, were mapped on different populations to facilitate joining the maps. Four genetic maps were developed using MapMaker V3.0 and JoinMap V3.0. The software CMap, a comparative map viewer, was used to align the four maps and identify potential errors based on consensus. JoinMap V3.0 was used to calculate marker order and recombination distances based on the consensus of the four maps. A total of 1,235 microsatellite loci were mapped, covering 2,569 cM, giving an average interval distance of 2.2 cM. This consensus map represents the highest-density public microsatellite map of wheat and is accompanied by an allele database showing the parent allele sizes for every marker mapped. This enables users to predict allele sizes in new breeding populations and develop molecular breeding and genomics strategies.

Bread↗

AppaDB: an AcedB database for the nematode satellite organism Pristionchus pacificus.

Pristionchus pacificus is a free-living nematode of the Diplogastridae family and was recently developed as a satellite system in evolutionary developmental biology. AppaDB, a P.pacificus database, was created (http://appadb.eb.tuebingen. mpg.de) to integrate the genomic data of P.pacificus, comprising the physical map, genetic linkage map, EST and BAC end sequence and hybridization data. This developing database serves as a repository to search and find any information regarding physical contigs or genetic markers required for mapping of mutants. Additionally, it provides a platform for the Caenorhabditis elegans community to compare nematode genetic data in an evolutionary perspective.

Animals↗

High-density genetic linkage maps of Phytophthora infestans reveal trisomic progeny and chromosomal rearrangements.

Detailed analysis of the inheritance of molecular markers was performed in the oomycete plant pathogen Phytophthora infestans. Linkage analysis in the sexual progeny of two Dutch field isolates (cross 71) resulted in a high-density map containing 508 markers on 13 major and 10 minor linkage groups. The map showed strong clustering of markers, particularly of markers originating from one parent, and dissimilarity between the parental isolates on linkage group III in the vicinity of the mating-type locus, indicating a chromosomal translocation. A second genetic map, constructed by linkage analysis in sexual progeny of two Mexican isolates (cross 68), contained 363 markers and is thus less dense than the cross 71 map. For some linkage groups the two independent linkage maps could be aligned, but sometimes markers appeared to be in a different order, or not linked at all, indicating chromosomal rearrangements between genotypes. Graphical genotyping showed that some progeny contained three copies of a homologous linkage group. This trisomy was found for several linkage groups in both crosses. Together, these analyses suggest a genome with a high degree of flexibility, which may have implications for evolution of new races and resistance development to crop protection agents.

Chromosome Mapping↗

A microsatellite genetic linkage map of human chromosome 13.

We have characterized 21 polymorphic (CA)n microsatellites for the development of a genetic map of chromosome 13. Fifteen markers were isolated from a flow-sorted chromosome 13 library, four CA repeats were derived from NotI-containing cosmid clones, and two polymorphic markers were described previously (J. L. Weber, A. E. Kwitek, and P. E. May, 1990, Nucleic Acids Res. 18: 4638; L. Warnich, I. Groenwald, L. Laubscher, and A. E. Retief, 1991, Am. J. Hum. Genet. 49(Suppl.): 372 (Abstract)). Regional localization for all of the markers was performed by amplification of DNA from five somatic cell hybrids containing different deletions of chromosome 13. Genetic markers were shown to be distributed throughout 6 of the 11 resolvable chromosomal subregions. Using data from nine families provided by the Centre d'Etude du Polymorphisme Humain (CEPH), a framework map of 12 of these 21 markers was developed. Six of the 12 markers form three pairs, with each two members of a pair being tightly linked, such that nine systems of markers can be distinguished. The average heterozygosity of these 12 markers is 0.75. The total length of the sex-averaged map is 65.4 cM (Kosambi), with an average distance of 8.2 cM between systems of markers (eight intervals). Seven remaining markers were placed provisionally into the framework map.

Alleles↗

RAPD-based genetic linkage maps of yellow passion fruit (Passiflora edulis Sims. f. flavicarpa Deg.).

A single cross between two clones of passion fruit (Passiflora edulis Sims. f. flavicarpa Deg., 2n = 18) was selected for genetic mapping. The mapping population was composed of 90 F1 plants derived from a cross between 'IAPAR 123' (female parent) and 'IAPAR 06' (male parent). A total of 380 RAPD primers were analyzed according to two-way pseudo-testcross mapping design. The linkage analysis was performed using Mapmaker version 3.0 with LOD 4.0 and a maximum recombination fraction (theta) of 0.30. Map distances were estimated using the Kosambi mapping function. Linkage maps were constructed with 269 loci (2.38 markers/primer), of which 255 segregated 1:1, corresponding to a heterozygous state in one parent and null in the other. The linkage map for 'IAPAR123' consisted of 135 markers. A total of nine linkage groups were assembled covering 727.7 cM, with an average distance of 11.20 cM between framework loci. The sizes of the linkage groups ranged from 56 to 144.6 cM. The linkage map for 'IAPAR 06' consisted of 96 markers, covering 783.5 cM. The average distance between framework loci was 12.2 cM. The length of the nine linkage groups ranged from 20.6 to 144.2 cM. On average, both maps provided 61% genome coverage. Twenty-four loci (8.9%) remained unlinked. Among their many applications, these maps are a starting point for the identification of quantitative trait loci for resistance to the main bacterial disease affecting passion fruit orchards in Brazil, caused by Xanthomonas campestris pv. passiflorae, because parental genotypes exhibit diverse responses to bacterial inoculation.

Chromosome Mapping↗

A 3347-locus genetic recombination map of sequence-tagged sites reveals features of genome organization, transmission and evolution of cotton (Gossypium).

We report genetic maps for diploid (D) and tetraploid (AtDt) Gossypium genomes composed of sequence-tagged sites (STS) that foster structural, functional, and evolutionary genomic studies. The maps include, respectively, 2584 loci at 1.72-cM ( approximately 600 kb) intervals based on 2007 probes (AtDt) and 763 loci at 1.96-cM ( approximately 500 kb) intervals detected by 662 probes (D). Both diploid and tetraploid cottons exhibit negative crossover interference; i.e., double recombinants are unexpectedly abundant. We found no major structural changes between Dt and D chromosomes, but confirmed two reciprocal translocations between At chromosomes and several inversions. Concentrations of probes in corresponding regions of the various genomes may represent centromeres, while genome-specific concentrations may represent heterochromatin. Locus duplication patterns reveal all 13 expected homeologous chromosome sets and lend new support to the possibility that a more ancient polyploidization event may have predated the A-D divergence of 6-11 million years ago. Identification of SSRs within 312 RFLP sequences plus direct mapping of 124 SSRs and exploration for CAPS and SNPs illustrate the "portability" of these STS loci across populations and detection systems useful for marker-assisted improvement of the world's leading fiber crop. These data provide new insights into polyploid evolution and represent a foundation for assembly of a finished sequence of the cotton genome.

Chromosome Mapping↗

A preliminary genetic linkage map of the Pacific abalone Haliotis discus hannai Ino.

Preliminary genetic linkage maps were constructed for the Pacific abalone (Haliotis discus hannai Ino) using amplified fragment length polymorphism (AFLP), randomly amplified polymorphic DNA (RAPD), and microsatellite markers segregating in a F(1) family. Nine microsatellite loci, 41 RAPD, and 2688 AFLP markers were genotyped in the parents and 86 progeny of the mapping family. Among the 2738 markers, 384 (including 365 AFLP markers, 10 RAPD markers, and 9 microsatellite loci) were polymorphic and segregated in one or both parents: 241 in the female and 146 in the male. The majority of these markers, 232 in the female and 134 in the male, segregated according to the expected 1:1 Mendelian ratio (alpha = 0.05). Two genetic linkage maps were constructed using markers segregating in the female or the male parent. The female framework map consisted of 119 markers in 22 linkage groups, covering 1773.6 cM with an average intermarker space of 18.3 cM. The male framework map contained 94 markers in 19 linkage groups, spanning 1365.9 cM with an average intermarker space of 18.2 cM. The sex determination locus was mapped to the male map but not to the female map, suggesting a XY-male determination mechanism. Distorted markers showing excess of homozygotes were mapped in clusters, probably because of their linkage to a gene that is incompatible between two parental populations.

Animals↗

The rat corpulent (cp) mutation maps to the same interval on (Pgm1-Glut1) rat chromosome 5 as the fatty (fa) mutation.

The autosomal recessive obesity mutations fatty (fa) and corpulent (cp) arose in separate rat strains, 13M and Koletsky, respectively. By complementation analysis, the two mutations appear to be in the same gene. The somewhat different phenotypes of fa/fa and cp/cp animals probably reflect the fact that the mutations are segregating on different rat strains. The fa mutation has been mapped to the interval between Pgm1 and Glut1 on rat Chr 5, but cp has not been mapped genetically. We mapped cp in 30 obese progeny of a LA/N-BN cp/+ intercross using microsatellite markers for these flanking genes. Cp maps to the same genetic interval as rat fa and mouse db. Cp is flanked by Glut1 and Pgm1: Pgm1-------- cp -------- Glut1 map distance (cM) 1.67 6.67 Thus, cp and fa map to the same approximately 8 cm interval of the rat genome. In conjunction with the complementation studies alluded to above, these findings indicate that cp and fa are mutations in the same gene (Lepr).

Adipose Tissue↗

RECORD: a novel method for ordering loci on a genetic linkage map.

A new method, REcombination Counting and ORDering (RECORD) is presented for the ordering of loci on genetic linkage maps. The method minimizes the total number of recombination events. The search algorithm is a heuristic procedure, combining elements of branch-and-bound with local reshuffling. Since the criterion we propose does not require intensive calculations, the algorithm rapidly produces an optimal ordering as well as a series of near-optimal ones. The latter provides insight into the local certainty of ordering along the map. A simulation study was performed to compare the performance of RECORD and JoinMap. RECORD is much faster and less sensitive to missing observations and scoring errors, since the optimisation criterion is less dependent on the position of the erroneous markers. In particular, RECORD performs better in regions of the map with high marker density. The implications of high marker densities on linkage map construction are discussed.

Algorithms↗

Single nucleotide polymorphisms for integrative mapping in the Turkey (Meleagris gallopavo).

When multiple genetic maps exist for a species, integration of these maps requires a set of common markers be genotyped across the individual mapping populations. In the turkey, three genetic maps based on separate mapping populations are available. In this study, SNP-based markers were developed for integrating the cDNA/RFLP-based map (1) with microsatellite markers of the second-generation turkey genome map (2). Forty-eight primer sets were designed and tested and 33 (69%) correctly amplified turkey genomic DNA by PCR. Putative SNPs were detected in 20 (61%) of the amplified gene fragments, and 10 SNP markers were subsequently genotyped by PCR/RFLP for segregation analysis. Eight SNP markers were incorporated into the turkey genetic map.

Animals↗

Construction of a genetic linkage map in man using restriction fragment length polymorphisms.

We describe a new basis for the construction of a genetic linkage map of the human genome. The basic principle of the mapping scheme is to develop, by recombinant DNA techniques, random single-copy DNA probes capable of detecting DNA sequence polymorphisms, when hybridized to restriction digests of an individual's DNA. Each of these probes will define a locus. Loci can be expanded or contracted to include more or less polymorphism by further application of recombinant DNA technology. Suitably polymorphic loci can be tested for linkage relationships in human pedigrees by established methods; and loci can be arranged into linkage groups to form a true genetic map of "DNA marker loci." Pedigrees in which inherited traits are known to be segregating can then be analyzed, making possible the mapping of the gene(s) responsible for the trait with respect to the DNA marker loci, without requiring direct access to a specified gene's DNA. For inherited diseases mapped in this way, linked DNA marker loci can be used predictively for genetic counseling.

Chromosome Deletion↗

An integrated genetic linkage map with 1,137 markers constructed from five F2 crosses of autoimmune disease-prone and -resistant inbred rat strains.

The rat (Rattus norvegicus) is an important experimental model for many human diseases including arthritis, diabetes, and other autoimmune and chronic inflammatory diseases. The rat genetic linkage map, however, is less well developed than those of mouse and human. Integrated rat genetic linkage maps have been previously reported by Pravenec et al. (1996, Mamm. Genome 7: 117-127) (500 markers mapped in one cross), Bihoreau et al. (1997, Genome Res. 7: 434-440) (767 markers mapped in three crosses), Wei et al. (1998, Mamm. Genome 9: 1002-1007) (562 markers mapped in two crosses), Brown et al. (1998, Mamm. Genome 9: 521-530) (678 markers mapped in four crosses), and Nordquist et al. (1999, Rat Genome 5: 15-20) (330 markers mapped in two crosses). The densest linkage map combined with a radiation hybrid map, reported by Steen et al. (1999, Genome Res. 9: AP1-AP8), includes 4736 markers mapped in two crosses. Here, we present an integrated linkage map with 1137 markers. We have constructed this map by genotyping F2 progeny of five crosses: F344/NHsd x LEW/NHsd (673 markers), DA/Bkl x F344/NHsd (531 markers), BN/SsN x LEW/N (714 markers), DA/Bkl x BN/SsNHsd (194 markers), and DA/Bkl x ACI/SegHsd (245 markers). These inbred rat strains vary in susceptibility/resistance to multiple autoimmune diseases and are used extensively for many types of investigation. The integrated map includes 360 loci mapped in three or more crosses. The map contains 196 new SSLP markers developed by our group, as well as many SSLP markers developed by other groups. Two hundred forty genes are incorporated in the map. This integrated map should allow comparison of rat genetic maps from different groups and thereby facilitate genetic studies of rat autoimmune and related disease models.

Animals↗

A genetic linkage map of the rat derived from recombinant inbred strains.

We have constructed a genetic linkage map in the rat by analyzing the strain distribution patterns of 500 genetic markers in a large set of recombinant inbred strains derived from the spontaneously hypertensive rat and the Brown-Norway rat (HXB and BXH recombinant inbred strains). 454 of the markers could be assigned to specific chromosomes, and the amount of genome covered by the mapped markers was estimated to be 1151 centimorgans. By including a variety of morphologic, biochemical, immunogenetic, and molecular markers, the current map integrates and extends existing linkage data and should facilitate rat gene mapping and genetic studies of hypertension and other complex phenotypes of interest in the HXB and BXH recombinant inbred strains.

Animals↗

A genetic linkage map with 16 RFLP loci on the distal long arm of human chromosome 6.

We have constructed a genetic linkage map of the distal long arm of human chromosome 6 with 16 polymorphic DNA loci, including six VNTRs, based on genotypic analysis in 40 CEPH pedigrees. The genetic map spans 31 cM and the distance is similar to that estimated by physical methods. The order of loci is basically consistent with physical localizations determined by fluorescence in situ hybridization. This map will be useful for isolation of putative tumor suppressor genes on chromosome 6q that are implicated in certain malignancies and will assist studies of genetic diseases.

Chromosomes, Human, Pair 6↗

Comparative mapping of genes from human chromosome 12 by genetic linkage mapping in cattle.

Loci from human chromosome 12 were mapped in cattle to compare the gene order between species. Polymorphisms were detected in cattle in six loci that had been mapped with high precision in humans. Four of these loci, LALBA, SLC2A3, SYT1, and TPI1, mapped to bovine chromosome 5, and one, PLA2G1B, mapped to bovine chromosome 17. The sixth locus, SLC2A3L, due to a fragment produced by the SLC2A3 primers, maps to the telomeric region of BTA18. The differences in gene order between human chromosome 12 and cattle chromosome 5, when these loci are added to others already mapped in cattle, show evidence of significant rearrangement in gene order requiring several evolutionary events. There is also evidence in cattle chromosome 5 of the interspersal of material conserved on human chromosome 22 into the material conserved on human chromosome 12, consistent with ZOOFISH analyses. This analysis indicates that the larger block near the centromere is conserved on the long arm of human chromosome 12 and the smaller block near the telomere is conserved as part of the short arm of human chromosome 12. The level of variation detected in the amplified cattle DNA was approximately 1 variant per 464 nucleotides of haploid DNA using single-strand conformation polymorphism analysis. This corresponds to a per individual level of 1 variant per 1, 961 nucleotides of haploid DNA. This confirms lower genetic variability in cattle compared to humans but indicates the potential for millions of single nucleotide polymorphisms in cattle.

Animals↗

Single tree genetic linkage mapping in conifers using haploid DNA from megagametophytes.

We report a unique application of the Random Amplified Polymorphic DNA (RAPD) technique for genetic linkage mapping of a single spruce tree using haploid DNA from megagametophyte tissue of individual seeds. Sixty-one segregating loci were analysed for reproducibility, inheritance and linkage. Forty-seven of the 61 markers were distributed into 12 linkage groups and covered 873.8 cM. The 14 markers not associated with any linkage group should be assigned to linkage groups as more markers are added to the map. This new approach quickly provides molecular genetic markers that are simple to evaluate for constructing genetic linkage maps and for other related genetic studies in forest tree species.

Base Composition↗