题目

_____, John returned to school from his hometown. A．The summer vacation being over        B．The summer vacation is over C．Because the summer vacation over       D．After the summer vacation being over 答案：A果蝇的翅形是由一对等位基因B和b控制，下表是有关果蝇翅形的三组杂交实验结果，请回答：（8分）(1)从表中                                              组合的实验可以推知，隐性性状是             。(2)乙组合中两个亲本基因型依次是       和              。(3)甲组合后代中，同时出现了长翅和残翅两种性状，这种现象在遗传学上称为 　　　　　。(4)表中                                                组合为测交实验。请写出该组合的遗传图解