Metzenberg R L, Stevens J N, Selker E U, Morzycka-Wroblewska E
Proc Natl Acad Sci U S A. 1985 Apr;82(7):2067-71. doi: 10.1073/pnas.82.7.2067.
The 5S rRNA genes of Neurospora crassa, unlike those of most organisms, are not tandemly arranged, and they are found imbedded in a variety of unique sequences. The 5S rRNA regions of most of the genes are of one type, alpha; however, several other "isotypes" (beta, gamma, delta, zeta, and eta) are also found. We asked whether Neurospora 5S rRNA genes are dispersed on a chromosomal scale and whether genes of different isotypes are spatially segregated. We identified, by DNA sequencing, 5S rRNA genes in 22 5S DNA clones, and we mapped these genes by conventional crosses by using restriction fragment length polymorphisms in their flanking sequences as genetic markers. The results show that the 5S rRNA genes are distributed on at least six of the seven chromosomes. Their location does not appear to be completely random. Some of them are closely linked. One of the chromosomes carries a disproportionate number of 5S rRNA genes of the most common structural type, alpha; another chromosome carries three of the four mapped beta 5S rRNA genes. None of the 5S rRNA genes studied maps close to the nucleolus organizer, the site of the genes that code for the three larger rRNAs.
与大多数生物不同，粗糙脉孢菌的5S rRNA基因并非串联排列，而是嵌于各种独特序列之中。大多数基因的5S rRNA区域属于一种类型，即α型；不过，也发现了其他几种“同型体”（β型、γ型、δ型、ζ型和η型）。我们探究了粗糙脉孢菌的5S rRNA基因在染色体水平上是否分散，以及不同同型体的基因在空间上是否分离。我们通过DNA测序在22个5S DNA克隆中鉴定出5S rRNA基因，并利用其侧翼序列中的限制性片段长度多态性作为遗传标记，通过常规杂交对这些基因进行定位。结果表明，5S rRNA基因分布在七条染色体中的至少六条上。它们的位置似乎并非完全随机。其中一些基因紧密连锁。有一条染色体携带了数量不成比例的最常见结构类型α型的5S rRNA基因；另一条染色体上则携带了已定位的四个β型5S rRNA基因中的三个。所研究的5S rRNA基因中，没有一个定位在核仁组织区附近，核仁组织区是编码三种较大rRNA的基因所在的位置。
