Kim J J, Farnir F, Savell J, Taylor J F
Department of Animal Science, Texas A&M University, College Station 77843, USA.
J Anim Sci. 2003 Aug;81(8):1933-42. doi: 10.2527/2003.8181933x.
This study was conducted to detect quantitative trait loci (QTL) affecting growth and beef carcass fatness traits in an experimental population of Angus and Brahman crossbreds. The three-generation mapping population was generated with 602 progeny from 29 reciprocal backcross and three F2 full-sib families, and 417 genetic markers were used to produce a sex-averaged map of the 29 autosomes spanning 2,642.5 Kosambi cM. Alternative interval-mapping approaches were applied under line-cross (LC) and random infinite alleles (RA) models to detect QTL segregating between and within breeds. A total of 35 QTL (five with genomewide significant and 30 with suggestive evidence for linkage) were found on 19 chromosomes. One QTL affecting yearling weight was found with genomewide significant evidence for linkage in the interstitial region of bovine autosome (BTA) 1, and an additional 19 QTL were detected with suggestive evidence for linkage under the LC model. Many of these QTL had a dominant (complete or overdominant) mode of gene action, and only a few of the QTL were primarily additive, which reflects the fact that heterosis for growth is known to be appreciable in crosses among Brahman and British breeds. Four QTL affecting growth were detected with genomewide significant evidence for linkage under the RA model on BTA 2 and BTA 6 for birth weight, BTA 5 for yearling weight, and BTA 23 for hot carcass weight. An additional 11 QTL were detected with suggestive evidence for linkage under the RA model. None of the QTL (except for yearling weight on BTA 5) detected under the RA model were found by the LC analyses, suggesting the segregation of alternate alleles within one or both of the parental breeds. Our results reveal the utility of implementing both the LC and RA models to detect dominant QTL and also QTL with similar allele frequency distributions within parental breeds.
本研究旨在检测影响安格斯牛和婆罗门牛杂交实验群体生长及牛肉胴体脂肪性状的数量性状基因座（QTL）。该三代定位群体由29个正反交回交和3个F2全同胞家系的602个后代组成，使用417个遗传标记构建了覆盖29条常染色体、跨度为2642.5 Kosambi cM的性别平均图谱。采用系间杂交（LC）和随机无限等位基因（RA）模型下的替代区间作图方法，检测品种间和品种内分离的QTL。在19条染色体上共发现35个QTL（5个具有全基因组显著连锁证据，30个具有连锁暗示证据）。在牛常染色体（BTA）1的间质区域发现一个影响一岁龄体重的QTL具有全基因组显著连锁证据，在LC模型下还检测到另外19个具有连锁暗示证据的QTL。这些QTL中许多具有显性（完全显性或超显性）基因作用模式，只有少数QTL主要是加性的，这反映了婆罗门牛和英国品种杂交中生长杂种优势明显这一事实。在RA模型下，在BTA 2和BTA 6上检测到4个影响出生体重的、具有全基因组显著连锁证据的QTL，在BTA 5上检测到影响一岁龄体重的QTL，在BTA 23上检测到影响热胴体重的QTL。在RA模型下还检测到另外11个具有连锁暗示证据的QTL。LC分析未发现RA模型下检测到的任何QTL（BTA 5上的一岁龄体重QTL除外），这表明一个或两个亲本品种内存在交替等位基因的分离。我们的结果揭示了同时应用LC和RA模型检测显性QTL以及亲本品种内具有相似等位基因频率分布的QTL的实用性。
