考研英語(yǔ)閱讀生物科技2)

1、Untilaboutfiveyearsagotheveryideathatpeptidehmonesmightbemadeanywhereinthebrainbesidesthehypothalamuswasastounding.Peptidehmonesscientiststhoughtweremadebyendocrineglsthehypothalamuswasthoughttobethebrains’onlyendocrineg

2、l.Whatismebecausepeptidehmonescannotcrossthebloodbrainbarrierresearchersbelievedthattheynevergottoanypartofthebrainotherthanthehypothalamuswheretheyweresimplyproducedthenreleasedintothebloodstream.Butthesebeliefsaboutpep

3、tidehmoneswerequestionedaslabatyafterlabatyfoundthatantiserumstopeptidehmoneswheninjectedintothebrainbindinplacesotherthanthehypothalamusindicatingthateitherthehmonessubstancesthatcrossreactwiththeantiserumsarepresent.Th

4、eimmunologicalmethodofdetectingpeptidehmonesbymeansofantiserumshoweverisimprecise.Crossreactionsarepossiblethismethodcannotdeterminewhetherthesubstancesdetectedbytheantiserumsreallyarethehmonesmerelycloserelatives.Furthe

5、rmethismethodcannotbeusedtodeterminethelocationinthebodywherethedetectedsubstancesareactuallyproduced.Newtechniquesofmolecularbiologyhoweverprovideawaytoanswerthesequestions.ItispossibletomakespecificcomplementaryDNA’s(c

6、DNA’s)thatcanserveasmolecularprobesseekoutthemessengerRNA’s(mRNA’s)ofthepeptidehmones.IfbraincellsaremakingthehmonesthecellswillcontainthesemRNA’s.Iftheproductsthebraincellsmakeresemblethehmonesbutarenotidenticaltothemth

7、enthecDNA’sshouldstillbindtothesemRNA’sbutshouldnotbindastightlyastheywouldtomRNA’sfthetruehmones.ThecellscontainingthesemRNA’scanthenbeisolatedantiserumstopeptidehmonesmay[A]havebeenstedinthebrainfalongperiodoftime.[B]p

8、laynoroleinthefunctioningofthebrain.[C]havebeenproducedinsomepartofthebodyotherthanthebrain.[D]haveescapeddetectionbymolecularmethods.3.Accdingtothetextconfirmationofthebeliefthatpeptidehmonesarecreatedinthebraininareaso

9、therthanthehypothalamuswouldfcescientiststo[A]rejectthetheythatpeptidehmonesaremadebyendocrinegls.[B]revisetheirbeliefsabouttheabilityofantiserumstodetectpeptidehmones.[C]inventtechniquesthatwouldallowthemtolocateaccurat

10、elybraincellsthatproducepeptidehmones.[D]developatheythataccountftheroleplayedbypeptidehmonesinthebrain.4.Whichofthefollowingismentionedinthetextasadrawbackoftheimmunologicalmethodofdetectingpeptidehmones[A]Itcannotbeuse

11、dtodetectthepresenceofgrowthregulatsinthebrain.[B]Itcannotdistinguishbetweenthepeptidehmonessubstancesthatareverysimilartothem.[C]Itusesantiserumsthatareunabletocrossthebloodbrainbarrier.[D]Itinvolvesapurificationprocess