研究生英语课件以及课后详细答案第六单元.ppt
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1、Unit SixIs It in the Genes?ByArthurAllenQuestions1.Doyouagree thathumanbehavior ispredetermined by genes?Why or whynot?2.What can affect a particular genespotentialaccordingtothearticle?3.Whatarefraternalandidenticaltwinsrespectively?What are their similaritiesanddifferences?TextIn 1993,a NationalCa
2、ncerInstituteresearchernamedDeanHamermadewhatseemedtobeanastonishingdiscoveryaboutthegenetics of human behavior.He had located a link to malehomosexualityontheXchromosome,HamerreportedinScience.Thestorywassplashedacrossfrontpagesaroundthecountry.Atlast,overlydotingmothersandearlycross-dressinggamesw
3、ereoffthehookandthepredilectionsofeveryonefromWaltWhitmantoLiberace could be explained by a few errant proteins.Hamersarticle,basedonanexaminationoftheDNAof40gaybrothers,ledtomass-marketbookdealsandminorcelebrity.Thereisonlyonesmall,under reported glitch:Hamers results have never beenreplicated.Twos
4、ubsequentstudiesshowedmuchweakerevidenceofagaygene;athird,publishedonApril23butovershadowedbythemassacreatLittletonthedaybefore,foundnoevidenceatall.“Thereisnohintortrendinthedirectionoftheinitialobservation,”GeorgeEbers,aCanadianinvestigatorinvolvedinthestudy,saidinScience.mass-market n.,adj,销售量大(的
5、),畅销(的)vt,大量销售er n.Aquicktrawlthroughtheheadlinesofthe1990sfindsasimilarfate for other front-page genetic breakthroughs.Despite much-publicized discoveries of genes for schizophrenia,manic-depression,alcoholism and bipolar disorder,the precise geneticcomponentoftheseillnessescontinuetoeludescience.T
6、hesamegoes for personality traits.The much-trumpeted discovery of a“novelty-seekinggene”in1996hasntbeenreplicatednorhavevarious“depressiongenes”.Thisisnottosaythatprogressisntbeingmadeinparsingthebiologicalcomponentsofbehavior.Butinanygivenperson,theinterplayofgenesandtheenvironmentisahorrendouslyco
7、mplexstory.Individualgenesproducequitesubtleeffects,andthemorewelearnaboutDNA,thecleareritisthatanyparticular genes potential can be shut down or enhanced bycomplexbiochemicalpathwayscontingentuponthingslikesleep,nutritionandstress.Bipolar:adj.电双极的;两极地区的Bipolar disorder depression 医(状态与抑郁状态交替的)躁郁症((
8、亦作manic-depressive illness)Adecadeagothefieldofbehaviorgeneticswasaflutterwiththehopethatmolecularbiologywouldhomeinonwhatmakeseachofustick.But“thefogisliftingveryslowly,”saysKennethKender,aprofessor of psychiatric genetics at Virginia CommonwealthUniversity in Richmond.“Weve learned that in psychia
9、tricdisorders,therearenosinglegenesofreallylargeeffect.Iftherewere,wedhavefoundthemalready.”Genesforcertainconditions,such as Huntingtons or sickle cell disease,are known as simpleMendeliantraitsbecausetheyfollowthestraightforwardmodelofinheritancenotedbytheAustrianmonkGregorMendellastcentury.“Mende
10、liantraitsarelikeatrumpetcall.Thegeneticsignalblastsright through,”says Kender.“But the genetic effects in mostbehavioral disorders and traits are like whispers in a busy trainstation.Itshardtodistinguishthemfromthebackgroundnoise.”home in on (靠信号、雷达等)导向目标追踪home industry 本国工业;手工业生产;家庭工业home instruct
11、ion 家庭辅导home landscape 家庭园景Home in on sth:to aim or move exactly towards sth.对准某物,朝某物移动.That behavior is a tricky business to predict was elegantlydemonstratedbyanotherstudypublishedinSciencethismonth.Agroupofresearchersatthreeuniversities-inOregon,upstateNewYorkandEdmonton,Alberta-ranasetofidentica
12、lexperimentsoneightdifferentmousestrains,eachbredtoshowdistinctbehavioralattributes.Theideawastoseewhethertheywouldactaccordingtotype.Theydidnt.Insometests,geneticallyidenticalmiceacteddifferentlydependedonthelabthattestedthem.Astrainofmicelackingareceptorfortheneurotransmitterserotonin-asubstancewh
13、ose imbalance has been implicated in various addictions andmood disorders-was expected to drink more alcohol and showmoreanxietythantheothermicestrains.Butallthreeteamsfoundthatthe serotonin-mutantsdidnt booze it up any more than theothers.AndallstrainsofmicetestedinAlberta,itturnedout,weremellower
14、than the New York and Oregon mice.Must be theweather,eh?Genetic programming,in other words,isnt nearly asefficientasscientistsmighthope.PeterW.Nathanielsz,aCornellUniversity obstetrician whose research focuses on the fetalenvironmentsofsheep,writesinanewbookthatsomeofthemost significant programming
15、of human health-and behavior,potentially-occurs in the womb.This isnt exactly a newobservation,butadvancesinneurosciencehighlightthefactthatthemigrationofneuronstothepreciseareaofthebrainwherethey belong during pregnancy is a dicey business that can beeasilydisrupted.Eveninahealthypregnancy,chanceha
16、salargeimpactontheprenatalformationofthebrain.Eventwinswithidenticalsetsofgeneshavebrainsthatlookdifferent.Whathappensinthewombisoneofthenewfrontiersofthenature-nurture debate.Epidemiology has already shown howimportantthewombcanbe.Overthepastseveraldecades,DavidBarkerofSouthamptonUniversityandother
17、researchershavebeenstudyingtheoutcomeofthethousandsofDutchbabiesconceivedorcarriedduringthehungerwinterof19441945,whentheNaziskeptfoodfromreachingpeopleinAmsterdamandthesurroundingareatopunishtheDutchfortheallied“BridgeTooFar”invasion.Immediatelyafterthewar,thispopulationsnutritionreturnedmoreor les
18、s to normal,but 50 years after their births,hunger winterbabies have much higher rates of diseases like diabetes thancontrols.Scientistsattributethehigherdiabetesratestothe“thriftyfetus”phenomenon-thefetuspancreaseswereprogrammedinthewomb to process much lower levels of glucose than becameavailablea
19、fterbirth.“Babieswhoprepareinthewombforathriftyexistence after birth pay the price if they live a life of over-consumption in a situation in which food is plentiful,”writesNathanielsz,who has observed the same phenomenon in animalexperiments.Ratswhosemotherseatlow-proteindietssufferfromvariousbehavi
20、oralandlearningproblems.Iftheratsarefemale,theyoftenpassthesetraitsontotheiroffspring,evenifthesecond-generationmothersdietisnormal,NathanielszwritesinhisbookLife in the Womb:theOriginofHealthandDisease.Malnourishedratstakemanygenerationsofhealthyeatingtoreturntonormal,inakindofLamarckianpatternofin
21、heritance,hewrites.“Theenvironmentofthewombisofextremeimportanceinbuildingthebodyandthebrain,”Nathanielsz says.“If things go wrong there can be apermanentpricetopay.”sufferer n.受苦难者;受害者;患者,病人suffer for 为.而受苦suffer from 患.病;受.苦suffer from cold and hunger 饥寒交迫Twinstudies,whichcomparethesharingoftraits
22、infraternalandidentical twins,have provided pretty convincing evidence of ageneticcomponenttomostaspectsofbehavior.Theyshowinstudyafterstudythatgeneticallyidenticaltwins,evenwhenseparatedformuch of their lives,are far more similar than fraternal twins ineverythingfromIQtoheartdiseasetoshyness.Twinst
23、udiesproducestatisticalestimatesofthegeneticcontributiontraitsforexample,thatIQis50to80percentgenetic.Butevenidenticaltwinscanhaveremarkably different womb environments.About a third of allidenticaltwinsarenourishedwithseparateplacentas,andinasmanyas10percentofthetwinswhoshareaplacenta,onetwinessent
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