首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
One reason why a sheep, a less well-understood experimental subject than the laboratory mouse, should have proved easier
One reason why a sheep, a less well-understood experimental subject than the laboratory mouse, should have proved easier
admin
2011-01-17
122
问题
One reason why a sheep, a less well-understood experimental subject than
the laboratory mouse, should have proved easier to clone may stem from
differences in the initial stages of the two species’ embryonic development.
Line After reaching maturity in the ovary of the mother, the unfertilized eggs of all
(5) mammals accumulate a supply of proteins, and the means of producing fresh
protein. In this way, the mammalian egg brings with it a larder for the embryo
to make use of until its own genes activate and supply this requirement
themselves. The sheep embryo disposes of its store properly and need not
depend on its own genes until the sixteen-cell stage, four cell divisions
(10) successive to fertilization, while in contrast, the mouse embryo commences this
process more precociously, becoming reliant on the activity of its own genes
after just the first division when the fertilized egg becomes two cells.
Therefore, a foreign nucleus introduced into a sheep egg exploits a respite in its
host’s biological development, allowing it to adapt to its new role before
(15) assuming genetic control.
Concomitantly, a nucleus introduced into a mouse egg must acclimatize
quickly for its genes to be able to direct embryonic development within a single
cell division, so perhaps there is insufficient time for the extensive re-
programming of compulsory gene activity. The human embryo is thought to rely
(20) on its own genes after three cellular divisions, which might or might not
provide time enough for a foreign nucleus to acclimate. However, were
scientists to comprehend the nature of the indispensable re-programming then
there is every likelihood that both mice and humans could be cloned.
Despite the long-standing availability of this technology, there has until
(25) recently been little interest in it. Some people suffering from infertility as a
result of rare hereditary diseases could produce offspring, but cloned individuals
may be at risk given scientists’ limited knowledge of the long term effects of
allowing an "old" adult cell nucleus to commence life again in an egg. The
nucleus of a skin cell could have accumulated a multitude of genetic mistakes of
(30) no consequence to its role in the skin, but the same cell could prove deleterious
in other tissues, or immensely increase the probability of the affliction with
cancer. The threat to general human health posed by cloning, as opposed to the
individual, is difficult to determine, but the risks are almost certainly lower
than those encountered in the effective inbreeding of consanguine marriages,
(35) and thus there are no scientific grounds per se for banning cloning. Like other
practices inconsequential to the physical well being of humanity, but generally
deemed undesirable on moral or social grounds, the prohibition of human
cloning will ultimately rest with only a simple pragmatic decision.
Information in the passage provides support for which of the following assertions concerning human cloning? Ⅰ. A better understanding of the genetic reprogramming process would not likely allow us to clone higher mammals. Ⅱ. The threat to public health that cloning presents should concern us more than that its threat to individual health. Ⅲ. The lack of interest in cloning owes less to a lack of technology than a skepticism toward its possible benefits.
选项
A、Ⅰ only
B、Ⅱ only
C、Ⅲ only
D、Ⅰ and Ⅲ only
E、Ⅰ,Ⅱ, and Ⅲ
答案
C
解析
转载请注明原文地址:https://kaotiyun.com/show/aLjO777K
本试题收录于:
GRE VERBAL题库GRE分类
0
GRE VERBAL
GRE
相关试题推荐
Youmust______thefactsandshouldnotrunawayfromthetruth.
Ican’tspeakJapanese,butIdowishI______.
Longbusridesareliketelevisionshows.Theyhaveabeginning,amiddle,andanend—withcommercialsthrownineverythreeor
Inancienttimesthemostimportantexaminationswerespoken,notwritten.IntheschoolsofancientGreeceandRome,testingus
Atthebeginningofthisterm,ourhistoryprofessor______alistofbooksforustoread.
Hedoesmorningexerciseseveryday______makehimstrong.
Myjobwastomakeclassroomobservationsandencourageatrainingprogramthatwouldenablestudentstofeelgoodaboutthemsel
Myjobwastomakeclassroomobservationsandencourageatrainingprogramthatwouldenablestudentstofeelgoodaboutthemsel
SURFEIT:
ThefirstchartbelowshowshowenergyisusedinanaverageAustralianhousehold.Thesecondchartshowsthegreenhousegasemi
随机试题
生产经营单位主要负责人在本单位发生重大生产事故时,没有立即组织抢救而逃匿的,除给予降职、撤职处分外,还处()以下拘留。
Mostparents,Isuppose,havehadtheexperienceofreadingabedtimestorytotheirchildren.Andtheymusthave【C1】______howd
佝偻病活动期应用大剂量维生素D治疗时应()
A.圆环病毒2型B.胸膜肺炎放线杆菌C.密螺旋体D.兔病毒性出血症病毒E.溶血性大肠杆菌兔瘟的病原是()。
房地产经纪人对客源资源有效利用的前提是()。
下列有关项目质量控制复核的说法中,正确的有()。
A.DoyouhavethebaggageclaimtagsB.I’vebeenwaitinginthebaggageclaimareaforonehourC.weareterriblysorryfort
Tradeiscentraltohumanhealth,prosperityandsocialwelfare.【R1】______Examplesoftradeindailylifearesoabundanttheys
求和平、促发展、谋合作是世界各国人民的共同心愿,也是不可阻挡的(irresistible)历史潮流。特别是世界多极化(multi—polarization)和经济全球化(economicglobalization)趋势的深入发展。给世界和平与发展带来了新
TopicMyViewonTravelForthispart,youareallowed30minutestowriteashortessayentitledMyViewonTravelfollowing
最新回复
(
0
)