问题 多项选择题

一个双链DNA分子为第一代,经过2次半保留复制后,在第三代的4个DNA分子中()

A.有2个DNA分子含有第一代DNA的脱氧核苷酸长链

B.有2个DNA分子不含有第一代DNA的脱氧核苷酸长链

C.第三代的4个DNA分子都含有第一代DNA的脱氧核苷酸长链

D.第三代的4个DNA分子都不含有第一代DNA的脱氧核苷酸长

答案

参考答案:A, B

解析:

DNA分子是半保留复制的,复制2次后,共有4个DNA分子中,其中只有两条是第一代脱氧核苷酸的长链,存在于两个DNA分子中,另外2个DNA分子不含有第一代DNA的脱氧核苷酸长链。

考点:本题考查DNA分子复制的知识。意在考查能理解所学知识的要点,把握知识间的内在联系的能力。

阅读理解

At school many things happen to us. We may feel excited when we have success in a school play. We may feel sorry if we lose an important game. We want to keep the memory for the rest of our lives.

How to keep the memory? Our English teacher, Miss Wang, has taught us a good way of remembering things to make our own yearbook. What is a yearbook? A yearbook is a kind of book which is used to keep the memory of exciting moments. It’s usually made at the end of the year.

Last December, we began to make our yearbook. First we chose the persons who had done something special, then some students interviewed (采访) them, some wrote down their stories, others took photos of them. Everyone in our class had something to do. Finally our teacher helped us to put the things together. We had our first yearbook.

All of us put a lot of love into making the yearbook. It is so wonderful that not only the students but also our parents and teachers will remember the special time for ever.

小题1:When we have success in a school play, we may feel ______

A.sorry

B.angry

C.excited

D.interested小题2:Miss Wang’s good way of remembering things is to ______

A.buy a new book

B.write down stories

C.take a lot of photos

D.make a yearbook小题3:A yearbook is made to ______

A.take notes

B.keep the memory

C.do our homework

D.remember English words小题4:Usually a yearbook is made in ______

A.January

B.February

C.May

D.December小题5:We made our first yearbook ______

A.without any help

B.without putting our love into it

C.with the help of our teacher

D.with the help of our parents

解答题