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I Olsaker

Publications and source records attributed to I Olsaker.

At least 37 records · Page 2Linked to original sources
PubMed1999

CAG repeats in various organisms studied by Southern blot analysis.

A 90-nucleotide (CAG)30, single-stranded DNA was used to probe Southern blots in order to indicate the quantity and distribution of long CAG repeats in selected genomes. Bovine and rat genomes were found to contain a particularly high content of CAG repeats, while the repeats were comparatively rare in the human genome. A particularly strong signal in the bovine genome was due to a CAG repeat associated with the 1.709 satellite. A similar element was found in goat and musk, but not in the other artiodactyls tested, suggesting that this particular CAG repeat developed some 10-20 million years ago within a 3.8-kb unit presently belonging to the satellite element and that this unit has later multiplied in the genome. Single-copy repeats could be discerned in yeast, but not in mammals. Thus the probe did not detect specific repeats in patients with CAG repeat diseases.

Animals↗
PubMed1999

Temporal changes in genetic variation of north European cattle breeds.

Temporal changes in genetic variation within and between 13 North European cattle breeds were evaluated using erythrocyte antigen systems and transferrin protein as genetic markers. Current data on allele frequency distributions of markers in large commercial and smaller endangered native cattle breeds were compared to data published during 1956 to 1975. Intrabreed genetic variation was quantified by conventional parameters (e.g. heterozygosity, average number of alleles per locus) and migration by the effective migration rate. The neighbour-joining dendrogram of relationships between old and present cattle populations was constructed using Nei's standard genetic distance. Variance effective population size was estimated from changes in allele frequencies over time. Comparison of old and new data indicated some significant changes in allele frequencies. In six of the breeds, a few low-frequency alleles in the old data were absent in the present samples. Heterozygosity remained stable in most breeds. The harmonic means for variance effective population size ranged between 30 and 257. Current results indicate that despite marked declines in total population sizes, North European native cattle breeds have retained a reasonably high genetic diversity. However, their genes contribute less than previously to genetic variation of Nordic production breeds. Commercial breeds do not appear to have a larger effective population size than native breeds. The present effective population sizes imply that Nordic breeds could have lost from 1 to 11% of their heterozygosity over a 20-40-year period.

Animals↗
PubMed1999

Comparison of milk protein allele frequencies in Nordic cattle breeds.

Allele frequencies at four milk protein loci were studied in five modern and 17 old Nordic cattle breeds in order to reveal variants that are characteristic for these populations. The B allele of CSN3, which has been associated with improved manufacturing properties of milk, showed significantly lower frequencies in modern production breeds than in old breeds of interest for conservation purposes. Characteristic frequencies of CSN1S1 (C), CSN2 (A2) and CSN3 (B) were found in Icelandic cattle, Swedish Mountain cattle, Northern Finncattle and Western Fjord cattle, which indicate a common origin of these populations. Further comparisons of allele frequencies in old Nordic breeds suggest sorting of these breeds into two groups with a northern and southern geographic location.

Alleles↗
PubMed1999

Heterozygosity excess at the cattle DRB locus revealed by large scale genotyping of two closely linked microsatellites.

A method for MHC DRB typing in cattle based on two closely linked and highly polymorphic microsatellites is described. The two microsatellites DRBP1ms and DRB3ms are located in intron 2 of the corresponding DRB gene. The very strong linkage disequilibrium between the two loci made it possible to establish DRB microsatellite haplotypes. The typing results with this method on reference samples followed closely that obtained with RFLP and direct sequence analysis of DRB3 exon 2. The method is well suited for large scale genotyping and was successfully applied for typing more than 600 unrelated animals representing 23 breeds. The data were used to test whether the observed DRB allele frequency distributions were consistent with that expected for selectively neutral alleles in populations at mutation-drift equilibrium. A significant heterozygosity excess was detected and there was an obvious trend across breeds towards a more even allele frequency distribution than expected. The deviation may be due to balancing selection acting on the DRB locus or by recent population bottlenecks.

Alleles↗
PubMed1999

Bovine chromosome 4 workshop: consensus and comprehensive linkage maps.

The report of the bovine chromosome 4 (BTA4) workshop is presented. Six laboratories contributed a total of 30,168 informative meioses from 62 loci. Twenty-two loci were typed by at least two independent laboratories and were used to construct a consensus linkage map of BTA4. The remaining 40 loci were subsequently incorporated into a comprehensive map. The sex-averaged consensus map covered 131.4 cM. The female map was 124.3 cM in length, while the male map was 134.3 cM. The comprehensive sex-averaged map spanned 141.6 cM. The length of the female and male comprehensive maps were 123.1 cM and 156.4 cM, respectively. Average genetic distance between loci was 6 and 2.3 cM for the consensus and comprehensive linkage maps, respectively.

Animals↗
PubMed1999

A high proportion of bovine blastocysts produced in vitro are mixoploid.

Fluorescence in situ hybridization with chromosome 6- and chromosome 7-specific probes was used to assess the extent of chromosome abnormalities in developing bovine blastocysts at 7-8 days after insemination in vivo or in vitro. Interphase nuclei (N = 10 946) were analyzed from 151 blastocysts produced in vitro and from 28 blastocysts recovered from superovulated animals. This revealed that 72% (109 of 151) of the in vitro-produced blastocysts were mixoploid, i.e., were a mixture of normal, diploid, and polyploid cells. However, only a small fraction of the total number of cells were chromosomally abnormal. Of the mixoploid blastocysts, 83% (91 of 109) contained less than 10% polyploid cells, 13% (14 of 109) contained 11-25% polyploid cells, and only 4% (4 of 109) of the blastocysts had more than 25% polyploid cells per blastocyst. In contrast, a significantly lower proportion (25%) of mixoploidy was found in 28 bovine blastocysts developed in vivo (p < 0.0001). All of the mixoploid blastocysts that had developed in vivo contained less than 10% polyploid cells. No entirely aneuploid blastocysts, i. e., blastocysts in which all cells had the same type of chromosome abnormality, were found in either of the groups. Taken together, the most common chromosome abnormalities observed were diploid-triploid mixoploidies and diploid-tetraploid mixoploidies. Thus, our results confirm earlier reports that morphologically normal bovine blastocysts developed in vivo are often mixoploids. We further show that in vitro-produced bovine blastocysts have a high rate of mixoploidy. Although the difference in mixoploidy rate detected in this study may not be general, it is an interesting phenomenon for further studies.

Animals↗
PubMed1997

Cosmid-derived markers anchoring the bovine genetic map to the physical map.

The mapping strategy for the bovine genome described in this paper uses large insert clones as a tool for physical mapping and as a source of highly polymorphic microsatellites for genetic typing, and was one objective of the BovMap Project funded by the European Union (UE). Eight-three cosmid and phage clones were characterized and used to physically anchor the linkage groups defining all the bovine autosomes and the X Chromosome (Chr). By combining physical and genetic mapping, clones described in this paper have led to the identification of the linkage groups corresponding to Chr 9, 12, 16, and 25. In addition, anchored loci from this study were used to orient the linkage groups corresponding to Chr 3, 7, 8, 9, 13, 16, 18, 19, and 28 as identified in previously published maps. Comparison of the estimated size of the physical and linkage maps suggests that the genetic length of the bovine genome may be around 4000 cM.

Animals↗
PubMed1997

Segregation studies and linkage analysis of Atlantic salmon microsatellites using haploid genetics.

A genetic marker map of Atlantic salmon would facilitate the identification of loci influencing economically important traits. In the present paper we describe five new Atlantic salmon microsatellites. Segregation studies and linkage analysis of these and previously published microsatellites were carried out in pedigrees consisting of diploid dams and haploid gynogenetic offspring. We confirm earlier reports that salmon microsatellites tend to have a higher number of repeat units than those of mammals. Linkage analysis revealed that three microsatellites belong to a linkage group spanning approximately 50 cM of the genome, whereas the remaining 10 markers seem to be unlinked.

Animals↗
PubMed1997

Sequence analysis of MHC class I alpha 2 domain exon variants in one diploid and two haploid Atlantic salmon pedigrees.

Genetic diversity in the second domain exon of Atlantic salmon (Salmo salar) major histocompatibility complex (Mhc) class I was investigated in two dams and nine of their haploid offspring by means of polymerase chain reaction (PCR) and DNA sequence analysis. A similar study was also performed on nine diploid offspring from one of these dams. The complex segregation patterns and sequence similarities between variants make definitive allele, haplotype and locus assignments difficult. There are, however, indications of six Mhc-Sasa class I loci and a fairly well-defined haplotype of four variants. One non-polymorphic variant present in most specimens could be a salmon analogue to the human non-classical loci.

Amino Acid Sequence↗
PubMed1997

FISH mapping of three bovine cosmids to cattle, goat, sheep and buffalo X chromosomes.

Contrary to extensive banding similarities of the autosomes, there are variations in the morphology as well as banding patterns of the X chromosomes of various species of bovidae family. We used three bovine X chromosome specific cosmid clones for fluorescence in situ hybridization mapping on cattle, goat, sheep, and river buffalo chromosomes to identify homologous regions in the genomes of the four species. The three cosmids (cIOBT 314, 945, and 1489) mapped to well spaced locations on buffalo X, and both arms of cattle X chromosome. However, of the three probes, cosmids cIOBT 314 and 1489 showed no hybridization signal on any of the goat-sheep chromosomes. Incidentally, the two cosmids show correspondence to those regions of the buffalo X chromosome which are proposed to be lost during the structural reshuffle of the latter, leading to sheep/goat X chromosomes. The lack of hybridization signal of the two cosmids in sheep and goat, therefore, indicates that these DNA sequences are most likely absent in the two genomes and probably correspond to the segments lost during evolution of their X chromosomes.

Animals↗
PubMed1997

Physical and linkage mapping of the bovine bone morphogenetic protein 1 on the evolutionary break region of BTA 8.

Bone morphogenetic protein 1 (BMP1) has been proposed as a regulatory molecule involved in the binding or activation of other BMP molecules. It has been described as being identical to the enzyme C-proteinase that processes procollagens to fibrillar collagens. A fragment containing an exon of the bovine BMP1 gene was amplified from an adapter-ligated genomic DNA library. The isolated bovine BMP1 fragment was assigned by fluorescence in situ hybridization (FISH) to bovine (BTA) chromosome 8q21, a region containing an evolutionary breakpoint between homology to human (HSA) chromosomes 8 and 9. The assignment to BTA 8 was confirmed by using a hybrid somatic cell panel. The 3' intron region of the amplified genomic BMP1 fragment showed a SSCP polymorphism, and linkage analysis in the International Bovine Reference Panel (IBRP) of families confirmed the boundary position of this gene. The BMP1 gene presents total linkage (theta = 0.00, Z = 3.61) with the lipoprotein lipase gene on BTA 8 and HSA 8 and a larger recombination fraction (theta = 0.11, Z = 5.03) with the marker GGTB2 on BTA 8 and HSA 9. Physical and genetic mapping of the bovine BMP1 gene contribute to narrow the boundary between the HSA 8 and HSA 9 homology segments on BTA 8 and to the comparative mapping between BTA 8, murine chromosome MMU 14, and HSA 8.

Animals↗
PubMed1996

Comparative FISH mapping of bovine cosmids to reindeer chromosomes demonstrates conservation of the X-chromosome.

Three X chromosome-specific bovine cosmids were used for fluorescence in situ hybridization mapping on reindeer (Rangifer tarandus) chromosomes, to test whether such large genomic clones could be used for comparative mapping across distantly related species. All three cosmids showed distinct unique hybridization sites on the reindeer X. Comparative map locations of these cosmids, together with the relative C-banding and genome size data on the X chromosomes of the two species, provide preliminary indications that the short and long arms of bovine X correspond, respectively, to the long and short arms of the reindeer X. The study also demonstrates that cosmid clones can be used successfully for comparative mapping across species that diverged 35 million years ago.

Animals↗