Osheim Y N, Miller O L
Cell. 1983 Jun;33(2):543-53. doi: 10.1016/0092-8674(83)90435-x.
Single-copy chorion genes coding for egg shell proteins are amplified in the follicle cells of Drosophila melanogaster egg chambers. Chromatin spreads of appropriately staged follicle cells reveal complex, multi-forked chromosomal structures in which one chromatin strand branches into two, which themselves branch out, and so on. In one micrograph, 13 strands originating from a single strand were observed. These structures can account for the maximal amplification occurring in the center of the domain, where the major chorion genes are located, and the decreasing amplification of flanking sequences to both sides. The amplification, high transcriptional rate, stage-specific expression, and correlation with known molecular sizes have allowed the putative identification of the single-copy, major chorion genes on the X chromosome and on chromosome III.
编码卵壳蛋白的单拷贝绒毛膜基因在黑腹果蝇卵室的卵泡细胞中被扩增。适当发育阶段卵泡细胞的染色质铺展显示出复杂的、多分支的染色体结构，其中一条染色质链分支成两条，这两条又各自分支，如此等等。在一张显微照片中，观察到从单条链起源的13条链。这些结构可以解释在该区域中心（主要绒毛膜基因所在之处）发生的最大扩增，以及两侧侧翼序列扩增的减少。这种扩增、高转录速率、阶段特异性表达以及与已知分子大小的相关性，使得人们能够推测性地鉴定出X染色体和Ⅲ号染色体上的单拷贝主要绒毛膜基因。
