问题 单项选择题

通过性菌毛介导将遗传物质从供体菌转移给受体菌的方式为

A.转化
B.接合
C.转导
D.溶原性转换
E.原生质体融合

答案

参考答案:B

解析:转化指受体菌直接摄取供体菌游离的DNA片段;接合指细菌通过性菌毛传递遗传物质(主要是质粒);转导则以温和噬菌体为载体;溶原性转换中,使细菌基因型发生改变的是整合到细菌染色体中的前噬菌体。

单项选择题
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Several years ago, I had a huge falling out with one of my best friends. So huge, in fact, that now I can’t even remember what happened.

In the past nine years, I’ve seen her twice, and each time we’ve been polite but distant. And that troubles me because we were once that close to each other. I’d like nothing more than to go back nine years, and continue our friendship. But how? How do you reconnect with friends you’ve lost throughout the years?

Linking to your past

The desire to reconnect with lost friend isn’t unusual. Why? Because friends link us to the past. Friends from years ago are custodians(监护人) of our past, says Sandy Sheehy, author of Connecting” The Enduring Power of Female Friendship.

Although you can’t share information about your past with friends you’ve met recently, you don’t have a shared history with them. So you wind up only telling them about your past, rather than sharing it with them.

But many people never try to reconnect. Women especially have trouble taking the first step. Shyness or fear that the other person doesn’t want to reconnect often stops many women. And that shouldn’t be. Your friends probably want to be in touch with you as much as you want to be in touch with them.

Searching for friends

Fortunately, finding lost friends isn’t as difficult as it once was, thanks to tools like the Internet. Our experts offer these suggestions for locating contact information:

Search Internet sites designed to locate people like classmates.com and switchboard.com.

Contact your high school or college alumni(校友)office to request current address information.

Surf online yellow pages. Check current phone records from your friend’s hometown.

Network with other friends who might have known your friend.

Get in touch with any of her relatives(亲戚), if you know where they live. If you know where she works, find the company’s web site and search the directory of personnel.

小题1:What ‘s the subject discussed in the passage?

A.How to make new friends.

B.How to rediscover friendships.

C.How to develop healthy friendships

D.How to keep in touch with friends.小题2:The underlined sentence “Friends from years ago are custodians of our past” means _____.

A.many years ago old friends kept something for us

B.in the past old friends took care of us

C.old friends are part of our life history

D.old friends know what wrong things we did in the past小题3:What makes us unwilling to reconnect old friends?

A.Lack of money

B.Shortage of time

C.Regret and shame

D.Fear and shyness小题4:How can we make contact with the lost friends?

A.By asking other friends of the information on your lost friends.

B.By searching your friends’ telephone number in the net.

C.By asking the local post office about your friends’ new address.

D.By putting an ad in your friends’ local town.