Taylor B A, Wnek C, Kotlus B S, Roemer N, MacTaggart T, Phillips S J
The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA.
Mamm Genome. 1999 Apr;10(4):335-48. doi: 10.1007/s003359900998.
Nine additional BXD recombinant inbred (RI) strains have been developed from the F2 cross of C57BL/6J and DBA/2J mouse strains. A tenth line stopped breeding in the F12 generation. F20 generation breeding pairs from the nine surviving strains and an F12 pair from the extinct line were genotyped at 319 genetic markers (primarily microsatellites) spanning most of the genome. Where typing data were lacking, the established set of 26 BXD strains also were genotyped at these same loci. The availability of these additional nine strains enhances the value of the BXD RI set for analysis of complex phenotypic traits. The proportion of loci still segregating at the F20 generation was found to closely approximate expectation, suggesting that selection favoring the retention of heterozygosity is not a strong factor. However, the number of crossovers between adjacent markers was frequently less than predicted from consensus map distances. A significant deficiency of recombinants was observed on Chrs 3, 4, 14, and X. On Chr 14, the estimated cumulative BXD map distance between the most proximal and distal markers was only 30.2 cM, compared with a distance of 60.0 cM in the consensus map. On the X Chr, the estimated and predicted cumulative distances were 38.8 and 69.5 cM, respectively. Over all chromosomes, the BXD RI map is 14.5% shorter than predicted from the consensus map. It is suggested that distances in some of the consensus maps are inflated. Alternatively, recombinant genotypes could be selected against during inbreeding owing to allelic interactions affecting fitness. The latter interpretation implies that relatively strong intrachromosomal epistasis is common.
另外九个BXD重组近交（RI）品系是由C57BL/6J和DBA/2J小鼠品系的F2杂交培育而成。第十个品系在F12代停止繁殖。对来自九个存活品系的F20代繁殖对以及来自灭绝品系的一对F12代进行了基因分型，共检测了319个遗传标记（主要是微卫星），这些标记覆盖了大部分基因组。在缺乏分型数据的情况下，还对已有的26个BXD品系在这些相同位点进行了基因分型。这另外九个品系的可用性提高了BXD RI品系集在分析复杂表型性状方面的价值。发现在F20代仍处于分离状态的位点比例与预期非常接近，这表明有利于保留杂合性的选择不是一个重要因素。然而，相邻标记之间的交叉数经常少于根据共识图谱距离预测的数量。在第3、4、14号染色体和X染色体上观察到重组体明显不足。在第14号染色体上，最近端和最远端标记之间估计的BXD累积图谱距离仅为30.2厘摩，而共识图谱中的距离为60.0厘摩。在X染色体上，估计的和预测的累积距离分别为38.8厘摩和69.5厘摩。在所有染色体上，BXD RI图谱比根据共识图谱预测的短14.5%。有人认为，一些共识图谱中的距离被夸大了。或者，由于影响适应性的等位基因相互作用，在近亲繁殖过程中可能会选择淘汰重组基因型。后一种解释意味着相对较强的染色体内上位性是常见的。
