题目

A.Once a day. B.Twice a week. C.Once a month. D.Twice a month. 答案：【答案】D【解析】【原文】W: Do you miss your mother, Tom?M: Of course. I send her an e-mail once a week. I ring her up twice a month.Q: How often does Tom ring his mother up?根据下表回答：遗传病名称正常婚配的后代患病率近亲婚配的后代患病率先天性聋哑1/118001/1500白化病1/730001/3600全色盲1/730001/4100(1)从上表可以看出，近亲婚配的后代患遗传病的可能性比正常婚配的要         。（2）某白化病患者父母都正常，以A表示正常基因，a表示白化病基因，则    为显性基因，该患者的基因组成是      ，其父母的基因组成均为        ，该患者白化病的基因来源是       ，而预防遗传病最简单有效的措施是             。