[单项选择]How are the mass media said to influence our ability to make decisions A. They disturb us by their prejudices. B. They make us doubt our own judgments. C. They make no contribution in this area. D. They make decisions which appear too complicated.
第3题: [单项选择]下列叙述中,能阐明等位基因作用的是() A. 控制同一性状的相同表现 B. 控制同一性状的不同表现 C. 不可能突变成相同基因 D. 性染色体上没有等位基因 参考答案:B 答案解析:等位基因是指在一对同源染色体的同一位置上控制相对性状的基因。由此可见,等位基因控制的是同一性状的不同表现。基因突变是不定向的,等位基因有可能突变成相同基因;同型性染色体(如XX),含有等位基因,异型性