问题 单项选择题

一般来说,癌细胞进行转移会分为几个阶段:一是侵犯,此时癌上皮细胞会松开癌细胞之间的连接,使之“重获自由”而能移动到其他地方;二是“内渗”,此时癌细胞穿过血管或淋巴管的内皮进入循环系统;三是“外渗”,此时经过循环系统之旅洗礼的幸存者会穿过微血管的内皮细胞到达其他组织;最后就是这些癌细胞的新大陆移民,在其他组织当中繁衍形成转移的恶性肿瘤。
此前这方面的研究都是将癌细胞注射入循环系统中,如此便缺少了与侵犯和内渗作用相关的基因研究。最近,美国一家研究所发表了与癌症转移早期相关的研究结果。
首先他们使用目前技术领先的微阵列技术对会转移的老鼠乳癌细胞的基因表现进行分析,从中找到了一个重要的转录因子Twist。这个转录因子在胚胎发育的某些过程中,肩负着引发细胞移动以及组织重组的任务,而类似的细胞移动以及组织重塑情形在肿瘤转移的时候也会发生。
他们发现Twist会使由钙黏附素E所调控的细胞黏附作用失效,产生上皮细胞的上皮一间质转化;且被阻断了Twist表现的癌细胞的转移程度会降低,在循环系统中的癌细胞数目也有减少的现象。另外,人类乳癌之一的侵犯性小叶癌当中也观察到Twist抑制了钙黏附素E的表现。
研究人员推测,癌细胞之所以能进行转移,可能是由于唤醒身体中沉睡已久的、负责胚胎早期型态发育的基因,导致相关程序的启动,从而获得可怕的转移能力。
未来在临床上也许能开发药物以抑制Twist这类基因的表现,避免肿瘤转移;或者可以藉由筛检这些基因,及早发现肿瘤未来的走向,并给予适当的治疗。

关于Twist,下列说法不符合文意的是( )。

A.引发细胞移动及组织重组
B.抑制某种细胞黏附作用
C.降低癌细胞的转移能力
D.引起上皮细胞的上皮一间质转化

答案

参考答案:C

解析: 由第三段中“这个转录因子在胚胎发育的某些过程中,肩负着引发细胞移动以及组织重组的任务”可知,A项正确:由第四段中的“Twist会使由钙黏附素E所调控的细胞黏附作用失效,产生上皮细胞的上皮一间质转化”可知,B、D项正确;由第四段中“被阻断了Twist表现的癌细胞”可知,并不是Twist降低癌细胞的转移能力。故本题答案为C。

完形填空
As Christmas is coming, there are presents to be bought, cards to be sent, and rooms to be cleaned. Parents are faced with difficult jobs of hiding presents from curious young children. If the gifts are large, this is sometimes a real    11 . On the Christmas Eve, young children find the excitement almost unbearable. They are torn between the wish to go to bed early so that Father Christmas will bring them presents quickly and the wish to   12  up late so that they will not   13  the fun. The wish for gifts usually proves stronger. But though children go to bed early, they often lie   14  for a long time, hoping to get a short look at Father Christmas.
Last Christmas, my wife and I   15  hid a few large presents in the storeroom. I   16  the moment when my son, Jimmy, would ask me where that new bike had come from, but fortunately he did not see it.
On Christmas Eve,   17   took the children hours to go to sleep. It must have been nearly   18  when my wife and I went quietly into their room and began   19  stockings. Then I pushed in the   20  I bought for Jimmy and left it beside the Christmas tree. We knew we would not get much sleep that night, for the children were   21  to get up early. At about five o’clock the next morning, we were   22  by loud sounds coming from the children’s room—they were shouting excitedly!   23   I had time to get out of bed, young Jimmy came riding into the room on his new bike, and his sister, Mary, followed close behind pushing her new baby carriage.   24  the baby arrived. He moved on the hands and knees into the room dragging a large balloon. We were woken up   25  by them at this time.
小题1:
A.questionB.matterC.problemD.business
小题2:
A.getB.stayC.standD.wake
小题3:
A.loseB.breakC.missD.leave
小题4:
A.awakeB.wakeC.asleepD.sleep
小题5:
A.hopefulB.busilyC.gladlyD.successfully
小题6:
A.likedB.fearedC.surprisedD.hated
小题7:
A.weB.theyC.ID.it
小题8:
A.morningB.midnightC.eveningD.daybreak
小题9:
A.fillingB.sewingC.mendingD.preparing
小题10:
A.presentB.stockingC.bikeD.tree
小题11:
A.goingB.sureC.gladD.excited
小题12:
A.troubledB.frightenedC.wokenD.shocked
小题13:
A.BeforeB.AfterC.UntilD.Since
小题14:
A.EvenB.AndC.SoonD.Then
小题15:
A.allB.nearlyC.happilyD.completely
单项选择题