Howell S H, Naliboff J A
J Cell Biol. 1973 Jun;57(3):760-72. doi: 10.1083/jcb.57.3.760.
Conditional "cycle-blocked" (cb) mutants of Chlamydomonas reinhardtii have been detected and isolated. These mutants exhibit normal vegetative growth at permissive temperature but are unable to complete a cell cycle (or a specified number of cell cycles) at restrictive temperature. A simple technique has been devised to determine the cell cycle stage in each mutant when the defective gene product, which ultimately affects cell division, completes its function. This stage is called the "block point", and is determined by scoring the residual cell division in an exponentially growing population after shift to temperature restrictive conditions. In the cb mutants isolated so far, block points representing many stages throughout the cell cycle have been found. Two categories of cb mutants are described here: one set which prevents the subsequent cell division when the cell encounters the block point after a shift to restrictive temperature, and another set which permits an additional round of cell division after the block point is encountered. The general applicability of block point analysis to other cell systems is presented.
莱茵衣藻的条件性“周期阻断”（cb）突变体已被检测和分离出来。这些突变体在允许温度下表现出正常的营养生长，但在限制温度下无法完成一个细胞周期（或特定数量的细胞周期）。已经设计出一种简单的技术来确定每个突变体中缺陷基因产物（最终影响细胞分裂）完成其功能时的细胞周期阶段。这个阶段被称为“阻断点”，通过对转移到温度限制条件后指数生长群体中的残余细胞分裂进行评分来确定。在迄今为止分离出的cb突变体中，发现了代表细胞周期中许多阶段的阻断点。这里描述了两类cb突变体：一类在转移到限制温度后细胞遇到阻断点时阻止后续细胞分裂，另一类在遇到阻断点后允许额外一轮细胞分裂。本文还介绍了阻断点分析在其他细胞系统中的普遍适用性。
