Geard C R
Environ Mutagen. 1983;5(3):319-28. doi: 10.1002/em.2860050310.
In root meristems of Tradescantia clone 02 (developed by Sparrow and his colleagues for mutation studies), X-rays interfere with the progression of cells through the cell cycle and induce chromosomal aberrations in a dose-dependent manner consistent with linear-quadratic kinetics. Sequential mitotic cell accumulations after irradiation indicate that sensitivity to aberration induction is probably greatest in cells from late S to early G2, with chromatid interchanges the most frequent aberration type and all aberrations consistent with initiation from the interaction between two lesions. The ratio of the coefficients in the linear (alpha) and the quadratic (beta) terms (alpha/beta) is equal to the dose average of specific energy produced by individual particles in the site where interaction takes place. The ratio alpha/beta for chromosomal aberrations is similar to that previously found for X-ray-induced mutation in Tradescantia stamen hairs, supporting the proposal that radiation-induced mutational events are due to chromosomal aberrations with interaction distances of about 1 micron. Abrahamson and co-workers have noted that both alpha/beta ratios appear to be related to nuclear target size and are similar for chromosomal and mutational endpoints in the same organism. These findings support this concept; however, it is apparent that any situation which diminishes yield at high doses (eg, mitotic delay) will primarily affect the beta component, resulting in low assessments of interaction site diameters.
在紫露草克隆02（由斯帕罗及其同事开发用于突变研究）的根分生组织中，X射线干扰细胞在细胞周期中的进程，并以与线性二次动力学一致的剂量依赖性方式诱导染色体畸变。辐照后连续的有丝分裂细胞积累表明，对畸变诱导的敏感性可能在从S期晚期到G2期早期的细胞中最大，染色单体互换是最常见的畸变类型，并且所有畸变都与两个损伤之间的相互作用引发一致。线性项（α）和二次项（β）的系数之比（α/β）等于相互作用发生部位单个粒子产生的特定能量的剂量平均值。染色体畸变的α/β比值与先前在紫露草雄蕊毛中X射线诱导的突变中发现的比值相似，支持了辐射诱导的突变事件是由于相互作用距离约为1微米的染色体畸变这一观点。亚伯拉罕森及其同事指出，两个α/β比值似乎都与核靶大小有关，并且在同一生物体中染色体和突变终点的比值相似。这些发现支持了这一概念；然而，很明显，任何在高剂量下降低产量的情况（例如有丝分裂延迟）将主要影响β成分，导致对相互作用位点直径的评估偏低。
