Refined positioning of a quantitative trait locus affecting somatic cell score on chromosome 18 in the German Holstein using linkage disequilibrium.
Combined linkage and linkage disequilibrium analysis (LALD) was conducted to more accurately map a previously reported quantitative trait locus (QTL) affecting somatic cell score on bovine chromosome 18. A grand-daughter design consisting of 6 German Holstein grandsire families with 1,054 progeny-tested genotyped sons was used in this study. Twenty microsatellite markers, 5 single nucleotide polymorphisms, and an erythrocyte antigen marker with an average marker spacing of 1.95 cM were analyzed along a chromosomal segment of 50.80 cM. Variance components were estimated and restricted maximum likelihood test statistics were calculated at the midpoint of each marker interval. The test statistics calculated in single-QTL linkage analysis exceeded the genome-wide significance threshold at several putative QTL positions. Using LALD, we were successful in assigning a genome-wide significant QTL to a confidence interval of 10.8 cM between the markers ILSTS002 and BMS833. The QTL in this marker interval was estimated to be responsible for between 5.89 and 13.86% of the genetic variation in somatic cell score. In contrast to the single-QTL linkage analysis model, LALD analyses with a 2-QTL model confirmed the position of one QTL, but gave no conclusive evidence for the existence or position of a second QTL. Ultimately, the QTL position was narrowed down considerably compared with previous results with a refined confidence interval of less than 11 cM.
Baes
C
C
Forschungsinstitut für die Biologie Landwirtschaftlicher Nutztiere, 18196 Dummerstorf, Germany.
Brand
B
B
Mayer
M
M
Kühn
C
C
Liu
Z
Z
Reinhardt
F
F
Reinsch
N
N
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000235:genetics*; D002874:Chromosome Mapping / Q000662:veterinary*; D002875:Chromosomes; D005260:Female; D015810:Linkage Disequilibrium; D008297:Male; D008413:Mastitis / Q000235:genetics / Q000662:veterinary*; D008892:Milk / Q000166:cytology*; D040641:Quantitative Trait Loci / Q000235:genetics*