Yee J K, Marsh R C
J Virol. 1981 Apr;38(1):115-24. doi: 10.1128/JVI.38.1.115-124.1981.
A restriction map of the bacteriophage T4 genome was aligned with the T4 genetic map. Included were the cleavage sites for BamHI, BglII, KpnI, PvuI, SalI, and XbaI. The alignment utilized the fact that the T4 genetic map had been oriented previously with respect to a T2/T4 heteroduplex map. DNA fragments from a BglII digestion of cytosine-containing DNA from a T4 dCTPase- denA denB(rIIH23B) alc mutant were hybridized with full-length chromosomal strands of bacteriophage T2, and the heteroduplexes were examined by electron microscopy. From their lengths and patterns of substitution and deletion loops, the heteroduplexes formed with 6 of the 13 BglII fragments could be unambiguously identified and positioned on the T2/T4 heteroduplex map. The ends of the T4 DNA strands in the heteroduplexes directly identified the location of 10 BglII cleavage sites. The remaining three BglII cleavage sites could be assigned to the T2/T4 heteroduplex map based on their relative locations on the restriction map. It was also possible to identify the source of the DNA strands (i.e., T2 or T4) in four previously unassigned deletion loops on the T2/T4 heteroduplex. Among the BglII fragments identified in heteroduplexes was the fragment containing the rIIH23B deletion; this deletion was used as the primary point of reference for alignment of the T4 restriction map with the T2/T4 heteroduplex map and, hence, with the T4 genetic map.
将噬菌体T4基因组的限制酶切图谱与T4遗传图谱进行了比对。其中包括BamHI、BglII、KpnI、PvuI、SalI和XbaI的切割位点。该比对利用了T4遗传图谱先前已相对于T2/T4异源双链体图谱进行定向的这一事实。来自T4 dCTPase-denA denB(rIIH23B) alc突变体含胞嘧啶DNA的BglII消化产物的DNA片段与噬菌体T2的全长染色体链杂交，然后通过电子显微镜检查异源双链体。根据它们的长度以及取代和缺失环的模式，可以明确识别由13个BglII片段中的6个形成的异源双链体，并将其定位在T2/T4异源双链体图谱上。异源双链体中T4 DNA链的末端直接确定了10个BglII切割位点的位置。其余三个BglII切割位点可根据它们在限制酶切图谱上的相对位置分配到T2/T4异源双链体图谱上。还能够在T2/T4异源双链体上四个先前未确定的缺失环中识别DNA链的来源（即T2或T4）。在异源双链体中鉴定出的BglII片段中，有一个包含rIIH23B缺失的片段；该缺失被用作将T4限制酶切图谱与T2/T4异源双链体图谱进行比对的主要参考点，从而也与T4遗传图谱进行比对。
