题干

下列对于遗传、变异和进化的分析错误的是(  )

A:非同源染色体之间染色体片段的交换属于染色体变异

B:基因自由组合定律的实质是:F1产生配子时,等位基因分离,非同源染色体上的非等位基因自由组合

C:地理隔离可阻止种群间基因交流,种群间基因库的差异可能导致生殖隔离

D:突变和基因重组会导致种群基因频率定向改变,自然选择也将导致基因频率定向改变

上一题 下一题 0.0难度 选择题 更新时间:2017-02-24 05:00:54

答案(点此获取答案解析)

D

同类题5

阅读下面短文,从短文后各题所给的四个选项(A、B、C、D)中,选出可以填入空白处的最佳选项。

    A beggar was sleeping in the doorway of a fruit shop. The shop owner felt angry. He walked up to him and 1 him to go away in a rude manner, but the beggar did not seem to2 him and lay still there. The shop owner got much3, shouting that he was a beggar in disguise (假装) and4 cheated passers-by for money by making use of their kindness. At that time, it was the busiest moment of a day and the market was5with shoppers. They all blamed the beggar for6. Showing fear, the beggar7his face in an old blanket. What he received was bitter8rather than help.

    The next morning, it was drizzling. An old man, who went to the market early, found the beggar 9on the ground. He woke the beggar up and 10 asked whether he was cold or not, but the beggar made no 11. Then the old man12his hands gently, saying that they felt13. With these words, he ran home in a hurry, returned with a pile of14, picked out a sweater and urged the beggar to15 it on again and again. Seeing what happened, many other passers-by surrounded the beggar and gave him change one after another, showing16for him. It was not long before the beggar received a handful of 17.

    In many cases our behavior may have a great18 on the people around us because they are likely to19us. Therefore, we should pay special attention to what we do and say, trying to infect others with positive words instead of 20 ones.