人类四肢是如何进化的?-凯发k8官网

人类四肢是如何进化的?
文章来源:未知 文章作者:enread 发布时间:2016-04-20 07:30 字体: [ ] 
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sharks, skates, and rays are oddities among the fish: they have 1 growing out of the gill arch, a small cradle of bones that supports the gills. this anatomical 2 has led to the proposal that the paired limbs of humans, and before that the paired 3 of fish, evolved from the 4 of gill arches in early fish. 6 evidence for this theory is offered in a new study led by j. andrew gillis, a royal society university research fellow at the university of cambridge, u.k., and a whitman center scientist at the 7 biological laboratory (mbl) in woods hole, mass. 
 
the study, published this week in development, demonstrates striking similarities in the genetic 8 used to pattern gill arch appendages (called branchial rays) and fins/limbs.
 
studying 9 of the little skate, gillis focused on the 5 sonic hedgehog, which produces a signaling protein whose function is well understood in the mammalian limb. 10, he found that sonic hedgehog's role in branchial rays closely parallels its role in the limb: it sets up the 11 of development and, later, maintains growth of the limb skeleton.
 
"the shared role of sonic hedgehog in patterning branchial rays and limbs may be due to a deep 12 relationship between the two," gillis says, "or it may simply be that two unrelated appendages independently use the same gene for the same function." 13 studies comparing the function of other 14 during branchial ray and fin/limb development will help to resolve this. gillis will continue his research at the mbl this summer using skates collected and supplied by the marine resources department.
 
"branchial rays will figure prominently in the story of the evolutionary origin of vertebrate animal appendages, either by shedding light on the evolutionary antecedent of paired fins/limbs, or by teaching us about the genetic 15 that animals can use to invent new appendages," gillis says.


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1 5ed0041aa3aab8c9e76c5d0b7c40fbe4     
n.附属物( appendage的名词复数 );依附的人;附属器官;附属肢体(如臂、腿、尾等)
参考例句:
  • the 11th segment carries a pair of segmented appendages, the cerci. 第十一节有一对分节的附肢,即尾须。 来自辞典例句
  • paired appendages, with one on each side of the body, are common in many animals. 很多动物身上有成对的附肢,一侧一个,这是很普遍的现象。 来自辞典例句
2 giwyp     
n.独特性,特色;特殊的东西;怪癖
参考例句:
  • each country has its own peculiarity.每个国家都有自己的独特之处。
  • the peculiarity of this shop is its day and nigth service.这家商店的特点是昼夜服务。
3 6a19adaf8b48d5db4b49aef2b7e46ade     
[医]散热片;鱼鳍;飞边;鸭掌
参考例句:
  • the level of tnf-α positively correlated with bmi,fpg,hba1c,tg,fins and iri,but not with sbp and dbp. tnf-α水平与bmi、fpg、hba1c、tg、fins和iri呈显著正相关,与sbp、dbp无相关。 来自互联网
  • fins are a feature specific to fish. 鱼鳍是鱼类特有的特征。 来自辞典例句
4 snfwo     
n.变化;改造;转变
参考例句:
  • going to college brought about a dramatic transformation in her outlook.上大学使她的观念发生了巨大的变化。
  • he was struggling to make the transformation from single man to responsible husband.他正在努力使自己由单身汉变为可靠的丈夫。
5 wgkxx     
n.遗传因子,基因
参考例句:
  • a single gene may have many effects.单一基因可能具有很多种效应。
  • the targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。
6 pgixp     
adj.遗传的,遗传学的
参考例句:
  • it's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
7 77izo     
adj.海的;海生的;航海的;海事的;n.水兵
参考例句:
  • marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
  • when the war broke out,he volunteered for the marine corps.战争爆发时,他自愿参加了海军陆战队。
8 zcwxr     
n.机械装置;机构,结构
参考例句:
  • the bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
  • the mechanism of the machine is very complicated.这台机器的结构是非常复杂的。
9 0e62a67414ef42288b74539e591aa30a     
n.晶胚;胚,胚胎( embryo的名词复数 )
参考例句:
  • somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段,而且其行为象胚。 来自辞典例句
  • evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句
10 ekpztw     
ad.不同寻常地,相当地
参考例句:
  • i thought she was remarkably restrained in the circumstances. 我认为她在那种情况下非常克制。
  • he made a remarkably swift recovery. 他康复得相当快。
11 sdxyz     
n.轴,轴线,中心线;坐标轴,基准线
参考例句:
  • the earth's axis is the line between the north and south poles.地轴是南北极之间的线。
  • the axis of a circle is its diameter.圆的轴线是其直径。
12 ctqz7m     
adj.进化的;演化的,演变的;[生]进化论的
参考例句:
  • life has its own evolutionary process.生命有其自身的进化过程。
  • these are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
13 6rvzt     
adj.进行中的,前进的
参考例句:
  • the problem is ongoing.这个问题尚未解决。
  • the issues raised in the report relate directly to age concern's ongoing work in this area.报告中提出的问题与“关心老人”组织在这方面正在做的工作有直接的关系。
14 01914f8eac35d7e14afa065217edd8c0     
n.基因( gene的名词复数 )
参考例句:
  • you have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
  • differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
15 d0db71d70348ef1c49f05f59097917b8     
n.机械( mechanism的名词复数 );机械装置;[生物学] 机制;机械作用
参考例句:
  • the research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
  • he explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》
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