Shioda M, Shiroya T
Cell Differ. 1987 Jan;20(1):11-6. doi: 10.1016/0045-6039(87)90460-x.
DNA was extracted from embryos of the sea urchin, Hemicentrotus pulcherrimus, at the S phase and examined by electron microscopy. We detected replication microbubbles with a mean size of 404 bases, in addition to replication macrobubbles of more than 1.0 kilobase (kb) in length. Seventy-five percent of the center-to-center distances of the microbubbles were 0.6-1.8 kb with a mean of 1.2 kb. Forty-five percent of the microbubbles were arranged as clusters of four or five microbubbles. These results suggest that at least 34% of the initiation sites for DNA replication are present on a DNA molecule in clusters in which the sites are arranged at 1.2-kb intervals.
从处于S期的海胆（Hemicentrotus pulcherrimus）胚胎中提取DNA，并通过电子显微镜进行检查。除了长度超过1.0千碱基（kb）的复制大泡外，我们还检测到平均大小为404个碱基的复制微泡。微泡中心到中心距离的75%为0.6 - 1.8 kb，平均为1.2 kb。45%的微泡以四个或五个微泡的簇状排列。这些结果表明，DNA复制的起始位点中至少34%存在于DNA分子上，这些位点以1.2 kb的间隔成簇排列。
