Population genetics of tandem repeats in centromeric heterochromatin: unequal crossing over and chromosomal divergence at the Responder locus of Drosophila melanogaster.
Population genetics of tandem repeats in centromeric heterochromatin: unequal crossing over and chromosomal divergence at the Responder locus of Drosophila melanogaster.
复制标题
着丝粒异染色质串联重复的群体遗传学：果蝇响应基因座的不等交换和染色体分歧。
DOI：
10.1093/genetics/135.2.477
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发表时间：
1993
期刊：
影响因子：
3.3
通讯作者：
Wu,CI
中科院分区：
文献类型：
--
作者：
Cabot,EL;Doshi,P;Wu,ML;Wu,CI
果蝇中的Responder（Rsp）基因座是分离畸变的靶基因座，已知由120 bp重复序列的串联阵列组成。在这项研究中，我们首先确定了大规模的Rsp基因座的分子结构，它延伸超过600 kb的标准敏感（cn bw）染色体上的区域。在该区域内，小的Rsp重复序列散布有非Rsp序列，占总序列的10-20%。我们从三条不同的染色体上分离并测序了32个Rsp克隆。主要结果如下：（1）来自同一条染色体的Rsp重复序列并不比来自不同染色体的Rsp重复序列更相似。这意味着在Rsp基因座上有比预期更多的同源交换，或者，D.在着丝粒异染色质上比在附近的常染色质上彼此分化最近。(2)重复序列通常具有二聚体结构，左半部分和右半部分之间的平均差异为16%。这些差异使我们能够很容易地识别不平等交换的产物。尽管两半之间的差异很大，但交换频繁发生，其中大多数都在两半之间的29 bp的同一性间隔内。因此，我们的数据支持的建议，重组取决于短的完整的身份，而不是长的一般同源性延伸。(3)频繁的不平等交叉事件掩盖了重复之间的系统发育关系;因此，任何单个重复的不同部分往往可能具有不同的系统发育历史。不平等交换的高比率也可能有助于解释Rsp基因座的进化动力学。
The Responder (Rsp) locus in Drosophila melanogaster is the target locus of segregation distortion and is known to be comprised of a tandem array of 120-bp repetitive sequences. In this study, we first determined the large scale molecular structure of the Rsp locus, which extends over a region of 600 kb on the standard sensitive (cn bw) chromosome. Within the region, small Rsp repeat arrays are interspersed with non-Rsp sequences and account for 10-20% of the total sequences. We isolated and sequenced 32 Rsp clones from three different chromosomes. The main results are: (1) Rsp repeats isolated from the same chromosome are not more similar than those from different chromosomes. This implies either that there are more homologous exchanges at the Rsp locus than expected or, alternatively, that the second chromosomes of D. melanogaster have diverged from one another more recently at the centromeric heterochromatin than at the nearby euchromatin. (2) The repeats usually have a dimeric structure with an average difference of 16% between the left and right halves. The differences allow us to easily identify the products of unequal exchanges. Despite the large differences between the two halves, exchanges have occurred frequently and the majority of them fall within a 29-bp interval of identity between the two halves. Our data thus support the suggestion that recombination depends on short stretches of complete identity rather than long stretches of general homology. (3) Frequent unequal crossover events obscure the phylogenetic relationships between repeats; therefore, different parts of any single repeat could often have different phylogenetic histories. The high rate of unequal crossing over may also help explain the evolutionary dynamics of the Rsp locus.