Barnes T M, Kohara Y, Coulson A, Hekimi S
Department of Biology, McGill University, Montréal, Quebec, Canada.
Genetics. 1995 Sep;141(1):159-79. doi: 10.1093/genetics/141.1.159.
The genetic map of each Caenorhabditis elegans chromosome has a central gene cluster (less pronounced on the X chromosome) that contains most of the mutationally defined genes. Many linkage group termini also have clusters, though involving fewer loci. We examine the factors shaping the genetic map by analyzing the rate of recombination and gene density across the genome using the positions of cloned genes and random cDNA clones from the physical map. Each chromosome has a central gene-dense region (more diffuse on the X) with discrete boundaries, flanked by gene-poor regions. Only autosomes have reduced rates of recombination in these gene-dense regions. Cluster boundaries appear discrete also by recombination rate, and the boundaries defined by recombination rate and gene density mostly, but not always, coincide. Terminal clusters have greater gene densities than the adjoining arm but similar recombination rates. Thus, unlike in other species, most exchange in C. elegans occurs in gene-poor regions. The recombination rate across each cluster is constant and similar; and cluster size and gene number per chromosome are independent of the physical size of chromosomes. We propose a model of how this genome organization arose.
秀丽隐杆线虫每条染色体的遗传图谱都有一个中心基因簇（在X染色体上不太明显），其中包含大多数通过突变定义的基因。许多连锁群末端也有基因簇，不过涉及的基因座较少。我们通过利用物理图谱中克隆基因和随机cDNA克隆的位置，分析全基因组的重组率和基因密度，来研究塑造遗传图谱的因素。每条染色体都有一个中心基因密集区域（在X染色体上较为分散），其边界清晰，两侧是基因贫乏区域。只有常染色体在这些基因密集区域的重组率降低。通过重组率来看，基因簇边界也显得清晰，并且由重组率和基因密度定义的边界大多但并非总是重合。末端基因簇的基因密度高于相邻的染色体臂，但重组率相似。因此，与其他物种不同，秀丽隐杆线虫的大多数交换发生在基因贫乏区域。每个基因簇的重组率是恒定且相似的；并且每条染色体上基因簇的大小和基因数量与染色体的物理大小无关。我们提出了一个关于这种基因组组织如何产生的模型。
