人的正常与白化病受基因A和a控制，正常与镰刀型细胞贫血症受基因B和b控制，两对基因分别位于两对常染色体上，假设白化病基因与相对应的正常基因相比，白化基因缺失了一个限制酶的切点。图一表示某家族遗传系谱图，图二表示甲、乙、丙3人白化基因或相对应正常基因的核酸分子杂交诊断结果示意图。据图回答下列问题。

(1)由图二可以判断出乙和丙的基因型分别是_________、_________。

(2)已知对③④进行核酸分子杂交诊断，其电泳结果都与甲的相同。⑥的基因型可能是_______，⑨是正常的可能性为________。

(3)白化病与镰刀型细胞贫血症这两种性状与基因的关系，所体现的基因控制性状的方式分别为：______；_______。

(4)如果要通过产前诊断确定⑨是否患有猫叫综合征，常用的有效方法是_______。

71.Vacations were once the prerogative of the privileged few, even as late as the 19th century. Now they are considered the right of all, except for such unfotrunate masses as, for example, the bulk of puplation in certain countries, for whom life, save for sleep and brief periods of rest, is uniterrupted toil.
Vacations are more necessary now than before because today the average life is less well-rounded and has become increasingly compartmentalized. 72. I suppose the idea of vacations, as we conceive it, must be incomprehensible to primitive peoples. Rest of some kind has of course always been a part of the rhythm of human life, but earlier ages did not find it necessary to organize it in the way that modern man has done. Holidays and feast days were sufficient.
With modern man’s increasing tensions, with the stultifying quality of so much of his work, this break in the year’s routine became steadily more necessary. 73. Vacations became mandatory for the purpose of renewal and repair. And so it came about that in the United States, the most self-indulgent of nations, the most tense and compartmentalized, vacations have come to take a predominant place in domestic conversation.