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1

Properties of the transmission-disequilibrium test for the detection of quantitative trait loci in livestock

100%
Szydlowski J., Liu Z., Wilda V.
Journal of Applied Genetics
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1998
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vol. 39
|
issue 4
309-319
EN
The transmission-disequilibrium test (TDT) is a model-free method to detect linkage between a marker and a trait locus. Originally developed to map disease genes in human genetics, this statistic has been recently extended to deal with quantitative characters. The emphasis of current research is on investigating statistical properties of the test applied to data from livestock populations. For various constellations of sample parameters, it is shown via simulation that the empirically derived null hypothesis distribution of TDT remains in good agreement with its asymptotic distribution while its power is satisfactory only for very close linkage. TDT is then applied to a real data set from milk production data of a dairy cattle population.
2

Genetic aspects of twinning in cattle

80%
Komisarek J., Dorynek Z.
Journal of Applied Genetics
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2002
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vol. 43
|
issue 1
55-68
EN
Twinning in cattle ranges from about 1% for beef breeds to about 4% for dairy breeds. The incidence of double births may have both positive and negative effects, which mainly depends on the purpose for which the cattle are raised. Because of freemartinism, as well as management problems connected e.g. with a greater risk of dystocia and retained placenta, it is an undesirable trait in dairy herds. In beef cattle, however, twinning can considerably increase the efficiency of production. Low heritability, a long generation interval for progeny testing, sex-limited expression and an unfavourable correlation with milk yield make twinning difficult to control by selection. Hence, it is the type of trait for which the identification of the genetic marker - quantitative trait loci (QTL) linkage and the implementation of marker-assisted selection in breeding strategies are expected to be especially beneficial. Searching for QTL influencing the reproductive rate in cattle was performed mainly in the US Meat Animal Research Center twinning herd and in the commercial Norwegian cattle population. Among several genome regions that appear to control twinning and ovulation rates, the most interesting seem to be chromosomes 5, 7, 19 and 23.
3

Novel linkage mapping approach using DNA pooling in human and animal genetics. II. Detection of quantitative traits loci in dairy cattle

80%
Pareek C. S., Pareek R. S., Walawski K., Pareek R. S.
Journal of Applied Genetics
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2002
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vol. 43
|
issue 3
309-318
EN
Selective DNA pooling is an advanced methodology for linkage mapping of quantitative trait loci (QTL) in farm animals. The principle is based on densitometric estimates of marker allele frequency in pooled DNA samples of phenotypically extreme individuals from half-sib, backcross and F2 experimental designs in farm animals. This methodology provides a rapid and efficient analysis of a large number of individuals with short tandem repeat markers that are essential to detect QTL through the genome ? wide searching approach. Several strategies involving whole genome scanning with a high statistical power have been developed for systematic search to detect the quantitative traits loci and linked loci of complex traits. In recent studies, greater success has been achieved in mapping several QTLs in Israel-Holstein cattle using selective DNA pooling. This paper outlines the currently emerged novel strategies of linkage mapping to identify QTL based on selective DNA pooling with more emphasis on its theoretical pre-requisite to detect linked QTLs, applications, a general theory for experimental half-sib designs, the power of statistics and its feasibility to identify genetic markers linked QTL in dairy cattle. The study reveals that the application of selective DNA pooling in dairy cattle can be best exploited in the genome-wide detection of linked loci with small and large QTL effects and applied to a moderately sized half-sib family of about 500 animals.
4

Application of microsatellities in genetic mapping of quantitative trait loci in farm animals

80%
Korwin-Kossakowska A.
Biotechnologia
|
1996
|
issue 2
178-183
EN
Microsatellites are tandem repeats of a simple sequence that occur abundantly and at random throughout most eukaryotic genomes.Mammalian microsatellite loci have been shown to be highly polymorphic due to variation in the number of repeat units.They are very good markers for quantitative traits loci (QTLs) mapping studies.Swedish Group from Agricultural University in Uppsala found evidence for QTLs on chromosome 4 with large effects on growth , fat deposition and length of the small intestine based on the analysis of genetic linkage between quantitative level and 105 genetic markers (68 microsatellities loci and 37 others markers).The localization of the gene affecting the ovulation rate and litter size on chromosome 6 in sheep has been documented on the basis of identification of genetic linkage between Booroola fecundity (FecB) gene and two microsatellite loci (OarHH55 and OarAE101) by a New Zealand scientist.Out of all types of actually known genetic markers microsatellites are most useful for QTLs mapping.
5

Analysis of associations of PIT1 genotypes with growth, meat quality and carcass composition traits in pigs

80%
Brunsch C., Sternstein I., Reinecka P., Bieniek J.
Journal of Applied Genetics
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2002
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vol. 43
|
issue 1
85-91
EN
PIT1 was chosen as a candidate gene to investigate its associations with growth, meat quality and carcass composition traits in the pig. PIT1 is known as the pituitary-specific activator of the growth hormone in several mammals. Furthermore, PIT1 is a positive regulatory factor of prolactin and thyroid-stimulating hormone b. PIT1 is a member of the POU-domain family of genes and is located on porcine chromosome 13. Two informative three-generation families of the University of Hohenheim were used for the presented investigations. The families were based on crosses of the European Wild boar (W) ? Pietrain (P) and Meishan (M) ? Pietrain (P). Each family included 310 F2 animals. A RsaI (PCR) RFLP described by YU et al. (1994) was used for genotyping the animals. Altogether over 50 parameters of growth, meat quality, carcass composition and stress susceptibility were evaluated concerning their associations with RsaI PCR-RFLP. The statistical model of association analyses was used including fixed effects of sex, family, PIT1 genotypes and covariate age at slaughter. Taking the significance level of p < 0.05 as the basis, fourteen traits of growth and carcass composition were associated with PIT1 genotypes in family W ? P. Results from this study suggest that there are contributions of PIT1 gene to variations in the analysed performance traits in pigs. The influence of PIT1 genotypes could not be confirmed under the supposition of a genome-wide test limit.
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