问题 选择题

人的细胞核有染色体的46条,经过两次分裂形成了4个细胞,每个细胞中的染色体数目是(  )

A.92条

B.46条

C.23条

D.数目不确定

答案

生物体的各种性状都是由基因控制的,性状的遗传实质上是亲代通过生殖细胞把基因传递给了子代,在有性生殖过程中,精子与卵细胞就是基因在亲子代间传递的桥梁,基因有规律地集中在细胞核内的染色体上,每一种生物细胞核内染色体的形态和数目都是一定的,如人的体细胞中含有23对(46条)染色体,水稻的体细胞内有12对染色体;在生物的体细胞中,染色体是成对存在的,基因也是成对存在的,分别位于成对的染色体上.在细胞分裂过程中,染色体复制加倍,随着分裂的进行,染色体分成形态和数目相同的两份,分别进入两个新细胞中.这样就保证了通过细胞分裂产生的新细胞与原细胞所含的遗传物质相同.人的细胞核中染色体数目是46,细胞正常分裂后,两个新细胞的染色体数目分别是46条和46条.

故选B

阅读理解

A new supermarket put on a notice inside the entrance. It said, “Remember, once a week, one of our customers(顾客) gets free goods(things that cost nothing). This may be your lucky day!” All the housewives who went to the supermarket had one great hope: to be the lucky customer who didn’t have to pay for her shopping.

For several weeks Mrs. Blake hoped to be the lucky customer. Unlike many other customers, she never gave up hope. The cupboards in her kitchen were full of things she did not need. She dreamed of the day, when the manager of the supermarket would come and say to her, “Madam, this is your lucky day and everything in your basket is free.”

One Friday morning, after she finished her shopping and had taken all the things to her car, she found that she had forgotten to buy tea. She went to the supermarket, got the tea and went towards the check-out. As she did so, she saw the manager of the supermarket come to her. “Madam,” he said, “congratulations! You are our lucky customer and everything in your basket is free!”

小题1:From the notice in the new supermarket, we know that       .

A.customers could buy things at lower prices once a week

B.the customer who bought the least goods didn’t have to pay

C.just one customer could get free goods once a week

D.the first customer who bought goods in the supermarket was the lucky one小题2: What was Mrs. Blake’s hope?

A.To buy something cheaper in the supermarket.

B.To see the manager of the supermarket.

C.To buy everything she needed in the supermarket.

D.To be the lucky customer.小题3: Why did Mrs Blake go back to the market after her shopping?

A.Because she wanted to see who would be the lucky customer.

B.Because she forgot to buy one more thing.

C.Because she had to pay for her shopping.

D.Because she wanted to get another chance to be the lucky customer.小题4:Which of the following is NOT TRUE according to the passage?

A.The manager of the market was a clever businessman.

B.In fact the notice for free goods was a trick (诡计).

C.Mrs. Blake’s dream came true at last.

D.Mrs. Blake did shopping every week in the past several weeks.小题5:What would Mrs. Blake probably say when she heard the manager’s words?

A.“Oh, my God!”

B.“How lucky I am!”

C.“Bad luck!”

D.“It’s very kind of you!”

多项选择题