European Molecular Biology Laboratory, Postfach 10.2209, D-6900 Heidelberg, FRG.
EMBO J. 1982;1(8):977-85. doi: 10.1002/j.1460-2075.1982.tb01281.x.
The organization of the 5S RNA gene cluster of Drosophila melanogaster is different in two Oregon R stocks that have been separated for a number of years. The Oregon R Yale population contains various different arrangements of the cluster. One of these is due to the insertion of a B104 element near one end of the cluster. Other arrangements lack the B104 insertion and have instead a variety of deletions originating in the vicinity of the B104 insertion site and removing from 0 to 60% of the 5S RNA genes without affecting nearby tRNA genes. In contrast, the Oregon R Heidelberg population has no B104 element in the 5S gene cluster and no heterogeneity in the arrangement of the cluster. We propose that transposable elements inserted at a genomic locus generate heterogeneity in a population at that locus due to excision of the element with and without accompanying deletions of flanking sequences. As a consequence, a fly population would accumulate a large number of deletions scattered throughout the genome in as many loci as contain transposable elements. We show further that D. melanogaster contains a large redundancy of 5S RNA genes since the 60% deletion of the cluster shows no visible phenotype when homozygous or when heterozygous against a total deletion of the entire 5S gene cluster.
黑腹果蝇的 5S RNA 基因簇在两个已分离多年的俄勒冈 R 品系中的组织方式不同。俄勒冈 R 耶鲁种群包含该簇的各种不同排列。其中一种是由于 B104 元件插入簇的一端附近。其他排列缺少 B104 插入，而是具有各种源自 B104 插入位点附近的缺失，从而去除了 0 到 60%的 5S RNA 基因，而不影响附近的 tRNA 基因。相比之下，俄勒冈 R 海德堡种群在 5S 基因簇中没有 B104 元件，并且簇的排列没有异质性。我们提出，转座元件插入基因组位点会由于元件的切除及其伴随的侧翼序列缺失而在该位点的群体中产生异质性。因此，果蝇种群将在包含转座元件的许多基因座中积累大量散布在整个基因组中的缺失。我们进一步表明，黑腹果蝇含有大量的 5S RNA 基因冗余，因为簇的 60%缺失在纯合或杂合时对整个 5S 基因簇的完全缺失没有可见表型。
