题干

在格里菲斯的肺炎双球菌转化实验中,加热杀死的S型细菌的某种成份能使R型细菌转化为S型细菌,R型细菌转化过程中遗传物质的变化与下列那种过程最为相似(   )

A:太空诱变育种获得高产品种

B:花药离体培养获得单倍体植株

C:农杆菌质粒侵入受体细胞

D:秋水仙素诱导染色体加倍

上一题 下一题 0.0难度 选择题 更新时间:2017-11-15 09:28:23

答案(点此获取答案解析)

C

同类题5

短文填空。从下面方框中选出10个单词,使短文意思正确通顺(每词限用一次)。

fight  they  for  suggest  healthy  if  fan  depend  lonely  what  cause  how

    One night, lots of people were running through the streets, shouting and throwing rocks. It was all about a soccer game. They were soccer ____ and they were angry that their team had lost an important game. They went completely out of control

    It's common ____ fans to get crazy. So many cities choose to put more police officers on the streets after big games. ____ makes fans so crazy?

    Some experts believe it goes back to a long-ago time when humans lived in tribes (部落). These tribes ____ each other for food, land and power (权力). You supported your tribe's warriors (武士) because your life ____ on them.

    Today's“warriors” are athletes (运动员). Cheering for ____ can bring out the same life-or-death feelings. That can be exciting and fun. It also ____ problems if the strong feelings last (持续) hours or days after a game has ended.

    On the other hand, some people say that being a sports fan can make you a happier and ____ person. Research shows that if you have a strong connection to a team, you might make strong connections with people. Many fans feel a sense of belonging to a group. They are less ____ and have more enjoyable social lives.

    ____ your favorite teams make you a bit crazy sometimes, it's only because you love them. And that's good — if you can remember that it's only a game.