首页
登录
职称英语
One reason why a sheep, a less well-understood experimental subject
One reason why a sheep, a less well-understood experimental subject
游客
2024-01-11
20
管理
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. [br] 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://tihaiku.com/zcyy/3353356.html
相关试题推荐
Thereason__________Ican’tcomeisthatIhavetoprepareforthecomingexam.A
That’sthereason_________Anncouldnotdoherpartofthejob.A、thatB、ofC、bec
Hedidn’tgointodetailsonthesubject,butjustspoke________.A、inparticular
Thereason________Ican’tcomeisthatIhavetoprepareforthecomingexam.A、f
Theprimarypurposeofthepassageisto______[br]Inresponsetoexperimental
Anexperimentalmicrowaveclothesdryerheatsneitherairnorcloth.Rather,it
Traditionally,decision-makingbymanagersthatisreasonedstep-by-stephasbee
Anexperimentwasdoneinwhichhumansubjectsrecognizeapatternwithinamatr
Thereasonmuchrefrigeratedfoodspoilsisthatitendsupoutofsightatthe
UnlikethelivesofPushkin,Gogol,Tolstoi,andDodtoevski,subjectsofotherT
随机试题
[originaltext]M:Whereareyougoingonvacationthissummer?W:Aniceplace
Itwasoncethoughtthatairpollutionaffectedonlytheareaimmediatelyar
药材延胡索的主要产地是A.浙江 B.安徽 C.广西 D.河北 E.云南
在拱式桥中,拱轴线两端点之间的水平距离为( )。 A、计算跨径 B、总跨
已知某房地产企业2016年第二季度的销售额资料如下表所示,在不考虑增长率的情况下
设立私募股权投资基金时要考虑一系列问题,当一只基金要在市场上募资时,普通合伙人通
小学班主任工作的中心环节是( )A、了解学生 B、班会活动 C、
中国证监会鼓励、支持诚实信用的公民、法人或者其他组织从事证券期货市场活动,实施诚
某公司将设备先后与甲乙丙三人订立了买卖合同,下列表述正确的有()。A.一般
220~500kV电网中,配置断路器失灵保护时,请回答以下问题。 以下应配置
最新回复
(
0
)