Waddell J, Wang X M, Wu M
Nucleic Acids Res. 1984 May 11;12(9):3843-56. doi: 10.1093/nar/12.9.3843.
Chloroplast DNA, isolated from a synchronized culture of Chlamydomonas reinhardii, was digested with restriction endonucleases and examined in the electron microscope. Restriction fragments containing displacement loops (D-loop) were photographed and measured to determine the position of replicated sequences in relation to the restriction enzyme sites. D-loops were located at two positions on the physical map of chloroplast DNA. One replication origin was mapped at about 10 kb upstream of the 5' end of a 16s rRNA gene. The second origin was spaced 6. 5kb apart from the first origin and was about 16.5 kb upstream of the same 16s rRNA. Initiations at those two sites were not always synchronized. Replication initiated with the formation of a D-loop resulting from the synthesis of one daughter strand. After a short initial lag phase, corresponding to the synthesis of 350 +/- 130 bp of one daughter strand, DNA synthesis then proceeded in both directions. Both D-loop regions were preferred binding sites of undetermined protein complexes.
从莱茵衣藻同步培养物中分离出叶绿体DNA，用限制性内切酶进行消化，并在电子显微镜下观察。对含有置换环（D环）的限制性片段进行拍照和测量，以确定复制序列相对于限制性酶切位点的位置。D环位于叶绿体DNA物理图谱的两个位置。一个复制起点定位在16s rRNA基因5'端上游约10 kb处。第二个起点与第一个起点相距6.5 kb，位于同一16s rRNA上游约16.5 kb处。这两个位点的起始并不总是同步的。复制始于由一条子链合成产生的D环的形成。在短暂的初始延迟期后，对应于一条子链350 +/- 130 bp的合成，DNA合成随后双向进行。两个D环区域都是未确定蛋白质复合物的优先结合位点。
