Analysis of chromosomal localization of loci controlling milk production traits in cattle

Analysis of the pattern of the chromosomal localization of quantitative trait loci (QTLs) is necessary for comprehensively understanding their functions. The chromosomal localization of QTLs controlling milk production traits has been studied in cattle chromosomes. The distribution of QTLs between chromosomes has proved to be binomial. Their distribution along each chromosome was, in general, uniform, except for the QTLs controlling the somatic cell score (SCS), which tended towards telomeric location. However, there are chromosomes either enriched with or particularly poor in QTLs. The QTL distribution patters are the most similar for the milk yield (M) and milk protein yield (P) and for milk fat yield (F) and milk fat content (%F). The pattern of the SCS QTLs stands out among those of other QTLs. The distance between the QTLs of contrasting traits is the shortest for M and P QTLs, longer for M and milk protein content (%P) QTLs, and still longer for M and %F QTLs, which may be explained by QTL pleiotropy, a common phenomenon in cattle.