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    【题目】在山羊遗传实验中,一黑色山羊与白色山羊杂交（白色与黑色由两对遗传因子控制且独立遗传）,子一代均为黑色。子一代个体间随机交配产生子二代个体中黑色∶浅黄色∶白色=12∶3∶1,则黑色个体和浅黄色个体中杂合子的比例分别为 （ ）

    A．1/6、2/3 B．1/8、1/3

    C．5/6、2/3 D．5/8、2/3

    【答案】C

    【解析】若用A和a、B和b表示相关的两对等位基因,由题意“子二代中黑色∶浅黄色∶白色=12∶3∶1”可推知,黑色为（9A B +3A bb或3aaB ）,浅黄色为（3aaB 或3A bb）,白色为aabb;在黑色个体中,纯合子有（1AABB+1AAbb或1aaBB）,其余都是杂合子,即杂合子占10/12=5/6;在浅黄色个体中,纯合子为（1aaBB或1AAbb）,其余为杂合子,即杂合子占2/3。

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