Maria Johansson

In situ hybridization mapping of the growth hormone receptor (GHR) gene assigns a linkage group (C9, FSA, GHR, and S0105) to Chromosome 16 in pigs

The completeness and utility of a gene map depend primarily on the uniform distribution of informative markers along the genome. Although gene mapping efforts during the past few years have resulted in a significant coverage of the porcine genome (Andersson et al. 1993), certain chromosomes/chromosomal regions still lack assigned markers. Chromosome (Chr) 16 is one of the chromosomes to which no genetic marker has yet been mapped. Recently, sequences homologous to the nucleolar organizer region (NOR) were localized by fluorescence in situ hybridization to the heterochromatic band in the middle of this chromosome (Bosma et al. 1991). There is, however, no confirmatory evidence that the hybridization site represents a NOR region, because the silver nitrate method (Bloom and Goodpasture 1976) does not demonstrate any staining on this chromosome. In the present study, we describe the chromosomal localization of the growth hormone receptor (GHR) gene to Chr 16 in pigs, using radioactive in situ hybridization (ISH). In addition, we also report the identification and subsequent assignment of a linkage group comprising the loci for GI-IR, complement factor 9 (C9) and follistatin (FSA), and the microsatellite S0105, to this chromosome. This linkage group has been identified as a part of an ongoing linkage analysis, by use of a three-generation pedigree. The family has been developed by crossing two Wild boars and eight Large White sows, and comprises 200 F 2 animals in total (Johansson et al. 1992). More than 120 genetic markers have now been typed in the pedigree (Ellegren et al. 1994, in preparation). Restriction fragment length polymorphisms (RFLPs) at the C9 and GHR loci have been detected in this pedigree (Johansson et al. in preparation). The GHR probe was a

Linkage maps of porcine Chromosomes 3, 6, and 9 based on 31 polymorphic markers

Linkage maps of porcine Chromosomes (Chrs) 3, 6, and 9, based on 31 polymorphic markers, are reported. The markers include 14 microsatellites, 12 RFLPs, three protein polymorphisms, and two blood group loci. The genetic interpretations of 11 RFLPs are documented. The markers were scored in a three-generation Wild Boar/Large White pedigree, and genetic maps were constructed on the basis of two-point and multi-point linkage analysis. Altogether the maps span a genetic distance of 216 cM, and previous physical assignments indicate that the linkage groups cover major parts of the three chromosomes. Significant differences in recombination rates between the sexes were observed for all three chromosomes. The recombination rate on the q arm of Chr 6 was markedly low. Sixteen loci are informative with regard to comparative mapping, that is, they have previously been mapped in the human and/or mouse genomes.

Assignment of the linkage group EAM-TYRP2-TPP2 to chromosome 11 in pigs byin situ hybridization mapping of the TPP2 gene

Restriction fragment length polymorphisms are described for the genes coding for tripeptidyl peptidase II (TPP2) and tyrosinase related protein II (TYRP2) in pigs. A linkage group comprising these loci and the locus for blood group M (EAM) was established by two-point lod score analysis in a three-generation pedigree. Multipoint analysis indicated the linear order EAM-1.1-TYRP2-8.4-TPP2 (recombination distances are given as Kosambi cM). The linkage group was assigned to porcine chromosome 11—the first on this chromosome—throughin situ hybridization mapping of the TPP2 gene. TPP2 is the first gene localized on this chromosome usingin situ hybridization.

Lack of significant associations with early career performance suggest no link between the DMRT3 "Gait Keeper" mutation and precocity in Coldblooded trotters

The Swedish-Norwegian Coldblooded trotter (CBT) is a local breed in Sweden and Norway mainly used for harness racing. Previous studies have shown that a mutation from cytosine (C) to adenine (A) in the doublesex and mab-3 related transcription factor 3 (DMRT3) gene has a major impact on harness racing performance of different breeds. An association of the DMRT3 mutation with early career performance has also been suggested. The aim of the current study was to investigate this proposed association in a randomly selected group of CBTs. 769 CBTs (485 raced, 284 unraced) were genotyped for the DMRT3 mutation. The association with racing performance was investigated for 13 performance traits and three different age intervals: 3 years, 3 to 6 years, and 7 to 10 years of age, using the statistical software R. Each performance trait was analyzed for association with DMRT3 using linear models. The results suggest no association of the DMRT3 mutation with precocity (i.e. performance at 3 years of age). Only two traits (race time and number of disqualifications) were significantly different between the genotypes, with AA horses having the fastest times and CC horses having the highest number of disqualifications at 3 years of age. The frequency of the AA genotype was significantly lower in the raced CBT sample compared with the unraced sample and less than 50% of the AA horses participated in a race. For the age intervals 3 to 6 and 7 to 10 years the AA horses also failed to demonstrate significantly better performance than the other genotypes. Although suggested as the most favorable genotype for racing performance in Standardbreds and Finnhorses across all ages, the AA genotype does not appear to be associated with superior performance, early or late, in the racing career of CBTs.