Cochran D G
Chromosoma. 1977 Jul 5;62(2):191-8. doi: 10.1007/BF00292639.
Metaphase I cells from heterozygotes in eight reciprocal chromosome translocation stocks of Blattella germanica (L.) have been examined and counted. The data show that three stocks have random disjunction (adjacent and alternate orientations are equally frequent), but the cell types adjacent-1, alternate-1, adjacent-2, and alternate-2 are present in a ratio of 2:1:1:2. Four stocks with directed disjunction have similar patterns, except for a heavy preponderace of alternate-2 cells. This difference is reflected in the finding that 60-65% of all cells in these interchanges are type II cells (alternate-2 plus adjacent-2), and individual percentages agree closely with percent directed disjunction is distinctly different in that the frequencies of both alternate-1 and alternate-2 cells are elevated and contribute to directed disjunction. It has also been demonstrated with two stocks that changes in disjunction frequencies can be brought about by genetic manipulation. These observations provide a better understanding of the differences between random and directed disjunction.
对德国小蠊（蜚蠊目）八个相互染色体易位品系的杂合子中期I细胞进行了检查和计数。数据显示，三个品系具有随机分离（相邻和交替取向同样常见），但相邻-1、交替-1、相邻-2和交替-2细胞类型的比例为2:1:1:2。四个具有定向分离的品系具有相似的模式，只是交替-2细胞占优势。这种差异反映在以下发现中：在这些互换中，所有细胞的60-65%是II型细胞（交替-2加相邻-2），个体百分比与定向分离百分比密切一致，明显不同的是交替-1和交替-2细胞的频率都升高，并导致定向分离。用两个品系也证明了分离频率的变化可以通过基因操作实现。这些观察结果有助于更好地理解随机分离和定向分离之间的差异。
