Yandeau-Nelson Marna D, Xia Yiji, Li Jin, Neuffer M Gerald, Schnable Patrick S
Interdepartmental Genetics Program, Genetics, Development and Cell Biology Department, Center for Plant Genomics, Iowa State University, Ames 50011, USA.
Genetics. 2006 Aug;173(4):2211-26. doi: 10.1534/genetics.105.052712. Epub 2006 Jun 4.
Tandemly arrayed duplicate genes are prevalent. The maize A1-b haplotype is a tandem duplication that consists of the components, alpha and beta. The rate of meiotic unequal recombination at A1-b is ninefold higher when a homolog is present than when it is absent (i.e., hemizygote). When a sequence heterologous homolog is available, 94% of recombinants (264/281) are generated via recombination with the homolog rather than with the sister chromatid. In addition, 83% (220/264) of homolog recombination events involved alpha rather than beta. These results indicate that: (1) the homolog is the preferred template for unequal recombination and (2) pairing of the duplicated segments with the homolog does not occur randomly but instead favors a particular configuration. The choice of recombination template (i.e., homolog vs. sister chromatid) affects the distribution of recombination breakpoints within a1. Rates of unequal recombination at A1-b are similar to the rate of recombination between nonduplicated a1 alleles. Unequal recombination is therefore common and is likely to be responsible for the generation of genetic variability, even within inbred lines.
串联排列的重复基因很普遍。玉米A1-b单倍型是一种串联重复，由α和β组件组成。当存在同源染色体时，A1-b处减数分裂不等位重组的速率比不存在同源染色体时（即半合子）高九倍。当有一个序列异源的同源染色体时，94%的重组体（264/281）是通过与同源染色体而非姐妹染色单体的重组产生的。此外，83%（220/264）的同源染色体重组事件涉及α而非β。这些结果表明：（1）同源染色体是不等位重组的首选模板；（2）重复片段与同源染色体的配对并非随机发生，而是有利于一种特定的构型。重组模板的选择（即同源染色体与姐妹染色单体）会影响a1内重组断点的分布。A1-b处不等位重组的速率与非重复a1等位基因之间的重组速率相似。因此，不等位重组很常见，并且可能是遗传变异产生的原因，即使在自交系中也是如此。
