问题 单项选择题

①科学家已经分离出一种看起来能决定人体衰老速度的基因序列。这一发现首次将DNA与人类寿命联系起来。②这项研究有望为创建筛查程序铺平道路,可用于检验哪些人更容易衰老,并在年轻时更容易患心脏病或其他疾病。③尽管这项突破不太可能带来大幅延长人类寿命的药物,但也许有助于延长那些由于自身基因而更易早逝的病人的寿命。④这项研究显示出了时间性衰老和生物性衰老的区别,其中生物性衰老取决于人体基因组成和生活方式,比如饮食组成和是否吸烟;两个年龄相同的人,其生物年龄可能会有十多年差异。⑤由桑尼教授带领的研究小组发现,一段普通DNA序列与人体的生物性衰老有密切关系。对近三千人的研究显示,约有38%的人带有遗传性基因变体,与没有这一基因序列的人相比,他们的生物年龄要老三到四岁;占总数7%的人带有两个这种基本变体,他们的生物年龄比没有该变体的人要老六到七岁。⑥通常被认为是老年病的发病年龄有很大的______,正是这一点促使研究者展开了这项研究。⑦我们身体中的大部分细胞都含有叫作染色体的DNA分子链。染色体在其两端有保护帽,叫做端粒。细胞每次分裂时,端粒会缩短,就像鞋带两端的塑料会被磨损一样。当端粒变得非常短时,细胞就无法正常工作,会显现衰老的征兆。⑧通过对血液样本的分析,桑尼发现,这些人具有与其年龄不相称的过短染色体端粒。而一种特定的基本序列在这些人中更常见。这段DNA位于3号染色体,与基因TERC相邻。⑨基因TERC可以制造出一种酶,能在端粒缩短时对端粒进行修复。携带有一个或两个该基因序列的人,在母体子宫中发育时,制造出的这种酶(端粒酶)可能比较少。这意味着,这些人在出生时端粒就比较短,所以更容易衰老。⑩科学家不可能通过增加人体中的端粒酶的数量来逆转人体老化的过程。人出生后,体内的端粒酶几乎全处于被抑制状态,但在癌细胞中端粒酶被激活,所以癌细胞就会无限分裂下去而不会死亡。因此桑尼指出:“激活端粒酶也许可以让你不得心脏病,但如果不加控制地激活端粒酶,你也许会得癌症。”

下列说法与该项研究中证明的人类提早衰老的原因无关的是( )。

A.老年病的发病年龄
B.体内缺少端粒酶
C.一两种基因序列异常
D.染色体两端的端粒太短

答案

参考答案:A

解析: 由“通常被认为是老年病的发病年龄有很大的跨度,正是这一点促使研究者展开了这项研究”可知“老年病的发病年龄”只是促使这项研究展开的一个出发点,并非是证明人类提前衰老的原因。因此A项无关,当选。

完形填空
完形填空.

     On a cold winter day,I waited in line to see my hero,Jack Canfield,the author of The Success
Principles
     During his talk,Jack__1__his wallet,pulled out a hundreddollar bill,and said,"Who wants this?"
__2__shot up in the audience;people leaned forward to see whom Jack would__3__.But I
jumped up,ran up the__4__to the stage,and grabbed the bill.As I was launching myself in the
air,thoughts__5__through my mind-was I about to be humiliated (羞辱) in front of 800 people?
Would they__6__security guards and take me from the stage?__7__my desire for bold action
was louder than any__8__voice.
     As I got the bill from his hand,he said,"That's it!We can't wait for the__9__to come to us.
We must take action to__10__what we want!"
     After his talk,I managed to formally meet Jack and boldly asked for his__11__email
address.Over the next months,I sent him emails__12__my vision and dreams with him.He
kindly emailed back lots of encouragement.But my life got__13__with other things.I stopped
emailing Jack.
     A year later,my dreams had worn away.I thought Jack would inspire me into action,like
a giant__14__that would show me the way.
     I emailed him,and then again-but got no__15__.As I sat down at my computer to check
my emails,I__16__woke up.What was I doing?I was waiting!Now I remembered the crowd,
most likely__17__that hundreddollar bill,while they sat__18__to their chairs.
     Usually we all have a "Jack"for whom we wait-whether it's a person,a place or a thing.
We__19__believe the gifts of life are just around the corner,and that everything will come
in a(n)__20__way.So we don't try.We give up.But as Wayne Gretzky said:"You'll always
miss 100% of the opportunities you don't take!" So I stopped waiting and started my
writing career.
     Now what are you waiting for?

( )1.A.stretched out
( )2 .A.Cheers
( )3.A.offer
( )4.A.path
( )5.A.raced
( )6.A.ask
( )7.A.And
( )8.A.careful
( )9.A.opportunities
( )10.A.attract
( )11.A.professional
( )12.A.disclosing
( )13.A.quick
( )14.A.arrow
( )15.A.news
( )16.A.gradually
( )17.A.desiring
( )18.A.lost
( )19.A.sincerely
( )20.A.difficult

B.reached for
B.Shouts
B.greet
B.road
B.started
B.call
B.So
B.doubtful
B.times
B.accept
B.secret
B.describing
B.busy
B.gate
B.notice
B.suddenly
B.claiming
B.glued
B.honestly
B.impressive

C.stuck to
C.Heads
C.like
C.steps
C.appeared
C.demand
C.But
C.meaningful
C.results
C.restore
C.public
C.presenting
C.full
C.exit
C.response
C.immediately
C.begging
C.opposed
C.falsely
C.early

D.handed in
D.Hands
D.choose
D.route
D.existed
D.order
D.Or
D.helpful
D.aims
D.create
D.personal
D.sharing
D.loose
D.entrance
D.reaction
D.slowly
D.worshiping
D.devoted
D.correctly
D.natural

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