题干

下列关于基因突变与染色体变异的叙述中,正确的是        

A:基因突变的频率很低,染色体变异可以用显微镜直接观察

B:基因突变发生在有丝分裂,染色体变异发生在减数分裂

C:染色体变异是定向的,基因突变是不定向的

D:基因突变是可遗传的,染色体变异是不可遗传的

上一题 下一题 0.0难度 选择题 更新时间:2016-06-07 07:37:43

答案(点此获取答案解析)

A

同类题4

阅读下列短文,然后从每小题A、B、C、D 中选出能回答所提问题或完成所给句子的最佳答案。    

    Some people believe that schools will no longer be necessary in the near future. They said that because of the Internet and other new technology, there is no longer any need for school buildings, classes or teachers. Perhaps this will be true one day, but if the world has no schools, I can't imagine how our society will be. In fact, we should learn how to use new technology to make schools better. We should invent a new kind of school that is linked to libraries, museums, science centers, labs and even companies. Technological companies should create(创造) learning programs for schools. Scientists or professors could give talks through the Internet. TV networks and local stations could develop programs about things students are actually studying in school. Labs could set up websites to show new technology so students could see it on the Internet.

    Is this a dream? No. There are already many cities where this is beginning to happen. Here the whole city is linked to the Internet, and learning can take place at home, at school, and in the office. Businesses provide programs for the schools and the society. The schools provide computer labs for people without their own computers at home. Because everyone can be on the Internet, older people use it as much as younger ones. And everyone can visit distant(远处的) libraries and museums as easily as nearby ones. How will this new kind of school change the usual way of learning? It is too early to be sure, but it is very exciting to think about it. Technology will change the way we learn; schools will change as well; and we will all learn something from the Internet.