Mapping of Quantitative Trait Loci in Norwegian Dairy Cattle / Kartlegging av Quantitative Trait Loci i Norsk Rødt Fe
The main aim of this thesis was to identify DNA regions with impact on important production traits in Norwegian Dairy Cattle by utilizing a set of different methods. Identification and characterization of the genes controlling such traits will yield important knowledge of the function and structure of the genome and how the genes interact with each other and the environment.
The thesis consists of four papers. In the fist paper, we proposed a novel method to identify regions affected by either natural selection at the gametic or zygotic level or by artificial selection for growth, by testing for distorted segregation of marker alleles from sire to sons. Chromosomes 6, 10 and 16 were found to harbor regions affected by artificial selection for growth, while regions on chromosomes 1, 7 and 17 were affected by either natural selection at the zygotic stage or random sampling. No indications of selection at the gametic stage were found.
The second paper describes a genome scan for quantitative trait loci (TL) affecting milk production. Six families with a total of 285 sons were analyzed for the traits milk yield, fat percentage, fat yield, protein percentage and protein yield by a multiple marker regression method. Putative QTL for one or more of the traits were detected on chromosomes 3, 5, 6, 11, 13, 18 and 20. Among these, the QTL on chromosomes 3, 6 and 20 are supported by the literature. The most interesting result was found on chromosome 6, where a QTL affecting fat and protein percentage, and to a lesser extent milk yield, were localized to a 16 cM interval.
Pr. desember 2004: Hanne Gro Olsen, Bovibank, c/o UMB, IHA, Postboks 5003, 1432 Ås
