问题 选择题

某菜农种了20株纯种(基因组合是aa)甜味菜椒,其中一株结了一个辣味菜椒,对此现象最合理的解释是

A.附近辣味菜椒的花粉传到了该菜椒花的柱头上

B.该菜椒子房壁的遗传物质发生了变化

C.该菜椒子房中受精卵的遗传物质发生了变化

D.该菜椒子房中珠被的遗传物质发生了变化

答案

答案:B

题目分析:变异是指子代与亲代之间的差异,子代个体之间的差异的现象.按照变异的原因可以分为可遗传的变异和不遗传的变异.可遗传的变异是由遗传物质改变引起的,可以遗传给后代;由环境改变引起的变异,是不遗传的变异,不能遗传给后代.某菜农种了20株纯种(基因组合是aa)的甜味菜椒,其中一个结了一个辣味菜椒,原因是该菜椒子房壁的遗传物质发生了改变.辣味菜椒的辣味物质存在于果皮的液泡内.绿色开花植物传粉受精完成后,子房发育为果实,子房壁发育为果皮,胚珠发育为种子,珠被发育为种皮.受精卵发育为胚.

A、附近辣味菜椒的花粉落到了该菜椒花的柱头上,只是受精卵中的遗传物质发生了变化,改变了胚的遗传物质,而子房壁的遗传物质没有发生变化,与辣味菜椒的形成有无关系,故不符合题意;

B、某菜农种了20株纯种(基因组合是aa)的甜味菜椒,其中一个结了一个辣味菜椒,原因是该菜椒子房壁的遗传物质发生了改变.与辣味菜椒的形成有关.故符合题意;

C、菜椒子房中受精卵中的遗传物质发生了变化,只是改变了胚的遗传物质,而子房壁的遗传物质没有发生变化,与辣味菜椒的形成有无关系,故不符合题意;

D、菜椒中子房中珠被的遗传物质没有发生了变化,只是改变了种皮的遗传物质,而子房壁的遗传物质没有发生变化,与辣味菜椒的形成有无关系,故不符合题意.

故选:B

完形填空

 完形填空(共20小题;每小题1.5分,满分30分)

阅读下面短文,掌握其大意,然后从36—55各题所给的四个选项(A、B、C和D)中,选出最佳选项,并在答题卡上将该项涂黑。

Attracting People to You

In West Virginia folklore there is a story of a country doctor. He was   36   late one night to    assist a woman who was about to give birth. By the time the doctor arrived at the farmhouse, things had   37   to a point where the doctor asked the husband to help him by holding a gas lantern up high in order to   38   the room.

Before long, the   39   mother delivered a healthy baby boy. As the father   40   the lantern, the doctor shouted an   41   to keep the lantern high: “We’re not done yet.”   42  , a second child appeared on the   43  , a healthy baby girl. Shaken by the unexpected arrival of twins, the father heard the doctor say once again, “We can’t   44   now. It looks as if it’s going to be triplets (三胞胎).” To which the   45   father, still holding the lantern high, replied, “Do you think it’s the light that’s   46   them?”

Light has a quality of attraction. I recently left my office door   47   late one afternoon in our mountain home and, at dusk, the   48   from within attracted a bird!

You, too, have a light that attracts … an inner light. Not   49   to the naked eye (肉眼), but obvious just the same. Some people   50   with a light of kindness. Others emit (散发,发射) a light of hope.

Almost all   51   are drawn to light, including humans. Do you want to attract people to you?   52   inner qualities can attract people like a warm fire on a   53   night. What will draw other people to you best cannot be   54   in any department store.

You may not always see it,   55   your light is shining through. And it’s one of your most attractive qualities!

36. A. called out     B. called on    C. called off   D. called back

37. A. happened     B. gone   C. turned D. progressed

38. A. decorate       B. darken       C. light   D. show

39. A. adventurous B. brave  C. humorous   D. dangerous

40. A. lowered       B. raised  C. weakened   D. brightened

41. A. order    B. idea    C. apology      D. excuse

42. A. Strangely     B. Shortly      C. Gradually   D. Lately

43. A. air B. screen C. scene  D. way

44. A. continue      B. help    C. argue  D. stop

45. A. worried       B. amazed      C. puzzled      D. amused

46. A. attracting     B. interesting  C. pulling       D. introducing

47. A. shut      B. locked C. open   D. wide

48. A. food     B. water  C. sound  D. light

49. A. comfortable B. visible C. available    D. valuable

50. A. shine    B. work   C. live     D. provide

51. A. creatures      B. birds   C. animals      D. plants

52.。A. Negative B. High   C. Positive      D. Poor

53. A. windy   B. cold    C. rainy   D. dark

54. A. exhibited     B. changed     C. exchanged  D. purchased

55. A. because B. since   C. but     D. if

单项选择题