问题 解答题

如图为克隆羊“多莉”的培养过程示意图,请回答:

(1)“多莉”不是由受精卵发育来的,她的身世与三只母羊有关.组成“多莉”的细胞核来自______羊的乳腺细胞,将该核注入______羊的去核卵细胞中,组成融合细胞,融合细胞分裂形成小小的胚胎后,再将这个胚胎移入______羊子宫内继续发育,一段时间后,小羊“多莉”出生.

(2)“多莉”是代孕母羊出生的,但它的长相却和______羊最为相似.由此可知,细胞中的遗传信息存在于______中,而储存遗传信息的物质是______,它的形状像一个______形的梯子.该遗传物质上,控制克隆羊“多莉”相貌等的一个个特定遗传信息的片段叫______.

答案

(1)利用电脉冲方法,使供体细胞核和受体卵细胞(无细胞核)融合,最后形成融合细胞.电脉冲可以产生类似于自然受精过程中的一系列反应,使融合细胞也能像受精卵一样进行细胞分裂、分化,从而形成胚胎细胞,最终发育成多莉.因此多莉不是由受精卵发育而来的,是体细胞发育形成的.三只羊与多莉的关系:母羊B为多莉提供了细胞核,也就是遗传物质.母羊A为多莉提供了去核卵细胞,也就是早期胚胎发育所需的营养物质.母羊C为多莉提供了胚胎发育的场所--子宫,也就是植入子宫内膜后,为多莉提供了营养物质.这个胚胎在C羊子宫内继续发育,一段时间后,小羊“多莉”出生.

(2)细胞核是遗传的控制中心,它里面含有遗传物质,能够传递遗传信息.B羊的细胞核内含有该绵羊全套的遗传基因,通过无性生殖产生的多莉羊,其遗传基因来自于B羊,所以克隆羊多莉的性状与B羊相似.通过这个实验,我们知道,细胞中的遗传信息在细胞核中,细胞核中能被碱性染料染成深色的物质叫做染色体,它是由DNA和蛋白质两种物质组成,DNA是主要的遗传物质,是由两条长链盘旋而成的规则的双螺旋结构,像一个螺旋形的梯子.DNA上有许多与遗传相关的片段,这些片段叫做基因.基因是DNA上具有遗传信息的片段.

故答案为:(1)B;A;C;(2)B;细胞核;DNA;螺旋;基因.

阅读理解

阅读理解。

     "Hey Dad," one of my kids asked the other day, "What was your favorite fast food when you were

growing up?"

     "We didn't have fast food when I was growing up," I told him. "All the food was slow.""Where did you

eat?""It was a place called 'at home,'" I explained. "Grandma cooked every day and when Grandpa got home

from work, we sat down together at the dining room table, and if I didn't like what she put on my plate I was

allowed to sit there until I did like it."

     Some parents never owned their houses, set foot on a golf course, travelled out of the country or had a

credit card (信用卡).

     My parents have never drove me to football practice. This was mostly because we never had heard of

football. I had a bicycle that weighed probably 50 pounds, and only had one speed. We didn't have a television

in our house until I was 11. I was 13 when I tasted my first pizza; it was called "pizza pie." When I bit (咬)

into it, I burned the roof of my mouth (上颚) and the cheese slid off, swung down, plastered (粘) itself

against my chin (下巴) and burned that, too. It's still the best pizza I ever had.

      I delivered newspapers, six days a week. The paper cost 7 cents, of which I got to keep 2 cents. I had

to get up at 4 a. m every morning. On Saturday, I had to collect the 42 cents from my customers. My favorite

customers were the ones who gave me 50 cents and told me to keep the change.

     If you grew up in a generation (一代) before there was fast food, you may want to share some of these

memories with your children and grandchildren.

     Growing up isn't what it used to be, is it?

1. By saying "All the food was slow", the writer implies (暗示) that ______.

A. when he was growing up, he never ate fast food

B. he didn't like fast food when he was growing up

C. his mother made food slowly

D. he had to wait for a long time for the fast food

2. From the writer's childhood life, we know that ______.

A. the writer lived a colorful life

B. the writer's parents treated him badly

C. the writer had to sell pizza to support his family

D. life was harder for him than it is for his children

3. The writer's purpose of writing this passage is to ______.

A. tell his children there was no fast food in the past

B. tell us that life has been changing

C. tell us how hard it is to deliver newspapers

D. make us understand the meaning of life

填空题