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用伸展DNA纤维的荧光原位杂交(Fiber-FISH)技术测定了5S rDNA和着丝粒DNA顺序RCS2在水稻广陆矮四号(Oryza sativa ssp indica cv Guangluai No4)基因组中的拷贝数. 为了确定拷贝数, 需要知道显微镜下一定长度DNA纤维所含碱基对数. 为此, 测量了两个已知碱基对数DNA序列的伸展纤维在显微镜下的长度. 其中供试BAC38D17的插入序列为136 kb, 其伸展纤维在显微镜下的长度为56.4 μm, 平均为2.41 kb/μm; BAC44B4全长为144.5 kb, 其伸展纤维的长度为55.7 μm, 平均为2.60 kb/μm. 这与Watson-Crick模型中B-DNA的2.97 kb/μm十分接近. 根据两个样本每微米平均碱基数, 即2.51 kb/μm的标准, 计算出5S rDNA的拷贝数约为686, 着丝粒DNA顺序RCS2约为286～1121拷贝.
The copy number of 5S rDNA and centromere DNA sequence RCS2 in the genome of Oryza sativa ssp indica cv Guangluai No4 was determined by using Fiber-FISH technique with stretched DNA fibers. In order to determine Copy number, you need to know the number of base pairs of DNA fibers of a certain length under the microscope.To this end, two known base pairs of DNA sequence length of the stretched fibers in the microscope where the insertion sequence for the test BAC38D17 136 kb, the length of the stretched fibers was 56.4 μm with an average of 2.41 kb / μm, the length of the stretched fibers was 144.5 kb with an average length of 55.7 μm (2.60 kb / μm), which was similar to that of Watson-Crick The B-DNA in the model is very close to 2.97 kb / μm, and the 5S rDNA copy number is about 686 based on the average number of bases per micrometer in each of the two samples, ie, 2.51 kb / μm. The centromeric DNA sequence RCS2 286 ~ 1121 copies.