Penman B W, Thilly W G
Somatic Cell Genet. 1976 Jul;2(4):325-30. doi: 10.1007/BF01538837.
The mutation of diploid human lymphoblasts by methylnitronitrosoguanidine (MNNG) was measured over the range of 0--45 ng of MNNG/ml of of medium. We found a 12-day lag in the phenotypic expression of 6-thioguanine resistance; the occurrence of this lag was independent of MNNG concentration. We hypothesize that the unexpectedly long lag period reflects a requirement for the loss of previously existing molecules of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) after mutation at the HGPRT locus.
在培养基中甲基亚硝基胍（MNNG）浓度为0 - 45 ng/ml的范围内，测定了其二倍体人类淋巴母细胞的突变情况。我们发现6 - 硫鸟嘌呤抗性的表型表达存在12天的延迟；这种延迟的出现与MNNG浓度无关。我们推测，出乎意料的长时间延迟反映了在次黄嘌呤 - 鸟嘌呤磷酸核糖转移酶（HGPRT）基因座发生突变后，需要消除先前存在的HGPRT酶分子。
