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Masle, Stela (2007): Multistage QTL mapping strategy in an advanced backcross cattle population. Dissertation, LMU München: Tierärztliche Fakultät



The aim of this study was to identify quantitative trait loci (QTL) affecting milk production traits in one advanced backcross Fleckvieh x Red Holstein population, that are identical by descent, according to both origin and effect.Genome wide scan and consequent QTL mapping by means of “selective DNA pooling” in the daughter design revealed two advanced backcross (Fleckvieh x Red Holstein) families segregating for QTL affecting protein percent (PP-QTL) on bovine chromosome 19 (BTA19). Identical by descent analysis indicated a 20 cM region as the most possible location of this QTL. After initial interval mapping in 20 granddaughter design families, six families segregating for PP-QTL in the same region were detected. PP-QTL segregating and related families were combined into a set of 11 granddaughter design families for intensive study performed with 21 microsatellite markers. Final interval mapping was able to confirm but not to refine the PP-QTL position. Combined linkage disequilibrium and linkage mapping refined the PP-QTL position. By this method we were able to locate highly significant PP-QTL in the region of 4-9 cM. Analyses performed on all available traits showed effects of the mapped QTL on milkability also. The analysis of estimated sires’ effects suggests rather one QTL with effect on both traits.