问答题
An ordinary scientist conducted a cross of shmoos double heterozygote with the same genotype AaBb. The phenotypic segregation rate of the filial generation he detected is 9:7. He was sure this is not a phenomenon of double recessive epistasis and it should be involved in a segregation rate of 9:6:1, and however, aabb is lethal. He thinks it would not be realizable to distinguish 9:7 and 9:6 by statistic method. but he cannot solve this problem. Can you help him?
【正确答案】首先，有无致死(aabb)，是会改变分离比的；其次，为证实有无致死基因，可用双杂合子亲本(AaBb)测交比数小的子代类型(这里假定是aaBB，aaBb，Aabb，AAbb和aabb)，从而暴露较大比例双隐性个体，与预期比例进行对比。
情形如下表示：
情形如下表示：
【答案解析】