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
考研
Got milk? If you do, take a moment to ponder the true oddness of being able to drink milk after you’re a baby. No other speci
Got milk? If you do, take a moment to ponder the true oddness of being able to drink milk after you’re a baby. No other speci
admin
2011-12-20
40
问题
Got milk? If you do, take a moment to ponder the true oddness of being able to drink milk after you’re a baby.
No other species but humans can. And most humans can’t either.
The long lists of food allergies some people claim to have can make it seem as if they’re just finicky eaters trying to rationalize likes and dislikes. Not so. Eggs, peanuts, tree nuts, fish, shellfish soy and gluten all can wreak havoc on the immune system of allergic individuals, even causing a deadly reaction called anaphylaxis.
But those allergic reactions are relatively rare, affecting an estimated 4% of adults.
Milk’s different.
There are people who have true milk allergies that can cause deadly reactions. But most people who have bad reactions to milk aren’t actually allergic to it, in that it’s not their immune system that’s responding to the milk. Instead, people who are lactose intolerant can’t digest the main sugar-lactose-found in milk. In normal humans, the enzyme that does so-lactase-stops being produced when the person is between two and five years old. The undigested sugars end up in the colon, where they begin to ferment, producing gas that can cause cramping, bloating, nausea, flatulence and diarrhea.
If you’re American or European it’s hard to realize this, but being able to digest milk as an adult is one weird genetic adaptation.
It’s not normal. Somewhat less than 40% of people in the world retain the ability to digest lactose after childhood. The numbers are often given as close to 0% of Native Americans, 5% of Asians, 25% of African and Caribbean peoples, 50% of Mediterranean peoples and 90% of northern Europeans. Sweden has one of the world’s highest percentages of lactase tolerant people.
Being able to digest milk is so strange that scientists say we shouldn’t really call lactose intolerance a disease, because that presumes it’s abnormal, instead, they call it lactase persistence, indicating what’s really weird is the ability to continue to drink milk.
There’s been a lot of research over the past decade looking at the genetic mutation that allows this subset of humanity to stay milk drinkers into adulthood.
A long-held theory was that the mutation showed up first in Northern Europe, where people got less vitamin D from the sun and therefore did better if they could also get the crucial hormone (it’s not really a vitamin at all) from milk.
But now a group at University College London has shown that the mutation actually appeared about 7, 500 years ago in dairy farmers who lived in a region between the central Balkans and central Europe, in what was known as the Funnel Beaker culture.
The paper was published this week in PLOS Computational Biology.
The researchers used a computer to model the spread of lactase persistence, dairy farming, other food gathering practices and genes in Europe.
Today, the highest proportion of people with lactase persistence live in Northwest Europe, especially the Netherlands, Ireland and Scandinavia. But the computer model suggests that dairy farmers carrying this gene variant probably originated in central Europe and then spread more widely and rapidly than non-dairying groups.
Author Mark Thomas of University College London’s dept of Genetics, Evolution and Environment says, "In Europe, a single genetic change.., is strongly associated with lactase persistence and appears to have people with it a big survival advantage. "
The European mutation is different from several lactase persistence genes associated with small populations of African peoples who historically have been cattle herders.
Researchers at the University of Mary land identified one such mutation among Nilo-Saharan-speaking peoples in Kenya and Tanzania. That mutation seems to have arisen between 2,700 to 6, 800 years ago. Two other mutations have been found among the Beja people of northeastern Sudan and tribes of the same language family in northern Kenya.
What is the relationship between "lactase" and "lactose" according to the passage?
选项
A、Lactase is indispensable to decomposing lactose.
B、They both can act as a kind of enzyme.
C、Lactase is the physical form of lactose.
D、Lactase can be used to synthesize lactos
答案
A
解析
由第六段可知,“lactose”是一种乳糖,“lactase”是人体内消化乳糖的酶,当人在2至5岁之间“lactase”停止分泌的时候,正常人则不能消化“lactose”。由此推断,lactase是分解lactose所必需的,A项正确。
转载请注明原文地址:https://kaotiyun.com/show/TDua777K
本试题收录于:
翻译硕士(翻译硕士英语)题库专业硕士分类
0
翻译硕士(翻译硕士英语)
专业硕士
相关试题推荐
receptorlanguage
Itisaresearchthatisguaranteedtodelightmen—andinfuriatethewomenintheirlives.Acontroversialnewstudyhasclaime
mobilenumberportability
researchethics
Theincreaseinleisuretime,thehigherstandardofliving,theavailabilityofcarstoawiderrangeofthepopulationand,pe
The______outcomeofthecontestvariesfrommomenttomoment.
Becausethehighseriousnessoftheirnarrativesresultedinpartfromtheirmetaphysics,Southernwriterwerepraisedfortheir
DemandAofnewequipmentroseBasbusinessimproved.UnlikeAirbus,BoeinghadalreadybeenoperatingCatfullcapacityandcoul
Haveyoueverfeltsoanxiousduringanexaminationthatyoucouldn’tevenputdowntheanswersyouknew?Ifso,youweresuffer
ThePaleolithiceraistheperiodofhistorycommonlyknownastheStoneAge.Itbeginswiththeappearanceofstonetoolsaroun
随机试题
设随机变量X服从参数为1/4的指数分布,则E(X)=【】
A.组织结构紊乱B.肿瘤细胞核分裂象多见C.肿瘤细胞形态不一致D.肿瘤细胞核的多形性良性肿瘤的异型性主要表现在
某企业销售商品一批,增值税专用发票上标明的价款为60万元,适用的增值税税率为17%,为购买方代垫运杂费为2万元,款项尚未收回。该企业确认的应收账款为()万元。
有一货轮在航行中与流冰相撞,船身一侧出现裂口,海水涌进,舱内部分货物遭浸泡,船长不得不将船就近驶上浅滩,进行排水和修补裂口,而后为了起浮,又将部分货物抛入海中,共损失25万美元,船长当即宣布为共同海损。问船舶达到目的港后,各有关方应如何进行分摊?设:船舶价
资料:A公司2011年12月31日资产负债表和利润表如下:要求:根据财务报表上资料计算2011年以下各个比率指标(计算结果保留两位小数):1.流动比率。2.速动比率。3.应收账款周转率。4.存货周转率。5.流动资产周转率。6.总资产周转
甲股份有限公司(下称“甲公司”)为上市公司,系增值税一般纳税人,适用所得税税率为25%,所得税采用资产负债表债务法核算,当年发生的可抵扣暂时性差异预计未来期间内能够转回;年末按净利润的10%计提法定盈余公积。甲公司2012年度实现利润总额6800万元(未
信息利用工作中,为了记录信息借阅情况可使用()
下列方法中,属于白盒法设计测试用例的方法的是()。
有以下程序:#includemain(){inta=0,b=0,C=0,d=0;if(a=1)b=1;c=2;elsed=3;printf("%d,%d,%d,%d\n",
J根据conformtothebeautystandards和blamethemfordoingso定位到J段。女性常常面临这样进退两难的境地:被期望能符合时代的审美标准,同时因为这样做而被谴责。本题句子是对原文的同义改写。
最新回复
(
0
)