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
Researchers have created male mice with no trace of a Y chromosome, supposedly the defining hallmark of being male. Reproduct
Researchers have created male mice with no trace of a Y chromosome, supposedly the defining hallmark of being male. Reproduct
admin
2019-08-27
32
问题
Researchers have created male mice with no trace of a Y chromosome, supposedly the defining hallmark of being male.
Reproductive biologist Monika Ward of the University of Hawaii in Honolulu and colleagues started with mice that have only one X chromosome (and no second sex chromosome). Normally those animals would develop as females. But when the researchers manipulated genes found on the X and another chromosome, the mice became males that could produce immature sperm. Those engineered males fathered offspring with reproductive assistance from the researchers, who injected the immature sperm into eggs, Ward and colleagues report in the Jan. 29 Science.
The experiments demonstrate that there are multiple ways to make males, says Richard Behringer, a developmental geneticist at MD Anderson Cancer Center in Houston. "They’ve done it without any Y chromosome gene information, " he says. "There’s not even a sniff of the Y around."
At first glance, the experiments would seem to suggest Y chromosomes aren’t necessary for reproduction, which hints that evolution may eventually show Y’s the door. "To me it is a paradigm of the decline and fall of the Y chromosome, " says reproductive biologist Jennifer Marshall Graves of La Trobe University in Melbourne, Australia.
But Ward and other researchers say the Y isn’t going anywhere and that interpreting the new results as the chromosome’s death knell is wrong. Because the Y-less males needed help to reproduce, "clearly we need the Y chromosome for full natural male reproduction, " says Mary Ann Handel, a reproductive biologist at the Jackson Laboratory in Bar Harbor, Maine.
Ward and colleagues had previously shown that two Y chromosome genes—Sry and Eif2s3y— are crucial for male mouse development. Sry is a master gene that turns on male developmental programming in early embryos. It turns on a gene called Sox9, which then sets off a biochemical chain reaction that leads to male development.
But in the new experiments, the researchers turned on Sox9 through other means. Activating Sox9 in a genetically female embryo will cause it to develop as a male, Ward and colleagues found. But those males didn’t make sperm. "The testes were empty, " says Ward.
In order to produce sperm, mice need the Eif2s3y gene, the researchers had previously discovered. In the new experiment, the mice were missing the gene because they didn’t have Y chromosomes. So researchers substituted a similar gene from the X chromosome called Eif2s3x. Only one copy of the Y version is needed to make immature, tailless sperm, but it takes at least five copies of the X version to do the same thing. "This indicates that the Y chromosome gene is the strong one, " says Ward.
Her research suggests that the Y chromosome has optimized production from genes that are necessary for making males. "Making just the right dose of male development factors is how the Y protects itself from evolutionary erasure, " Ward says. "Our work does not support that the Y chromosome will disappear."
Graves disagrees. Ward’s work is "a lovely example of how you can lose even a really important gene, " she says. At least two species of rodents have already jettisoned their Y chromosomes entirely. Primates, including humans, don’t have Eif2s3y genes on their Y chromosomes. The new work may help explain how primates get along without the gene, Graves suggests, and the research may "give us useful information about what happens at the end of the life of the Y chromosome".
What can be the best title for this passage?
选项
A、Mice Can Be Male Without the Y Chromosome
B、The Artificial Reproduction of Mice
C、The Mysterious Y Chromosome in Mice
D、The Male and Female Mice
答案
A
解析
本题为文章标题题。纵观全文可知,全文围绕研究人员如何培育没有Y染色体的雄性老鼠这一话题展开。A项“没有Y染色体的老鼠能发育成雄性老鼠”,最准确地概括了全文主旨。因此,选择A项。
转载请注明原文地址:https://jikaoti.com/ti/O0NYFFFM
0
考博英语
相关试题推荐
Smoking,whichmaybeapleasureforsomepeople,isaseruioussourceofdiscomfortfortheirfellows.【C1】______,medicalautho
Thewordhospiceishundredsofyearsold.ItcomestousfromthetimecalledtheMiddleAgesinEurope.Religiousgroupsthen
Youaresupposedtowritealettertotheeditorofajournalinyourfield,thankinghimforsuggestionsandadviceforyourpa
Obesitygenerallyisdefinedasanaccumulationoffat(adiposetissue)beyondwhatisconsiderednormalforaperson’sage,sex,
Justfourbitsofinformationcollectedfromashopper’screditcardcanbeusedtoidentifyalmostanyone,researchershavefou
Americanstodaydon’tplaceaveryhighvalueonintellect.Ourheroesareathletes,entertainers,andentrepreneurs,notschola
Ironically,theintellectualtoolscurrentlybeingusedbythepoliticalrighttosuchharmfuleffectoriginatedontheacademic
IfImaybeso______astoadviseyou,myopinionisthatyoushouldnotreplytohisletter.
Hehadwanteda25%raiseinpay,butaftertalkingtohisboss,hedecidedthata5%raisewouldhaveto______.(2002年中国人民大学考博
Insomecountriespreschooleducationinnurseryschoolsorkindergartens______the1stgrade.(2002年3月中国科学院考博试题)
随机试题
darkandsmoky
患者,女性,40岁,进行性背部疼痛。全身消瘦乏力1年。检查:第6胸椎后突畸形,局部有压痛及叩痛;X线检查示胸椎6、7间隙变窄,上下缘模糊;红细胞沉降率第一小时末为60mm。临床诊断为
对房地产经纪服务费的管理主要是从()方面进行。
下列不属于基金管理人应当履行的职责的是()
下面不属于有规则游戏的是()。
潜伏需求是指相当一部分消费者对某种商品或服务有强烈的需求,而现有产品或服务又无法使之满足的一种需求状况。根据上述定义,以下最能体现“潜伏需求”的是:
Happyhoursarenotnecessarilyhappy,nordotheylastforanhour,buttheyhavebecomeapartoftheritualoftheofficewor
Internet协议第4版(IPv4)为整个Internet提供了基本的通信机制,但随着应用的发展,迫切需要对IPv4进行更新,新一代的IP协议已被正式命名为IPv6。在IPv6中,每个地址有(1)个八位组,为方便网络管理人员阅读、管理,采用(2)进制加冒
在窗体上画一个名为Checkl的复选框,如果在窗体启动事件中编写语句”Checkl.Enabled=False”,则运行后复选框的状态为()。
To______thestructuralimbalancesinthebudget,andalsointheeconomytheAdministrationhasgivenitssupporttoaconstitut
最新回复
(
0
)