no support!
扫描二维码进行跟读打分训练
Study: IdenticalTwinsAreNotGeneticallyExactCopies
Anewstudysuggeststhatidenticaltwinsarenotexactlythesamegenetically. Identicaltwinsaretwobabiesthatcomefromthesamefertilizedegg.
ScientistsinIcelandexaminedDNAfrom 387 pairsofidenticaltwins, theirparents, children, husbandsorwives.
Theexaminationsledtheteamtofind "earlymutationsthatseparateidenticaltwins," leadresearcherandgeneticistKariStefanssonsaid. HeisaprofessorattheUniversityofIcelandandfounderofthecompanydeCODEgenetics.
MutationsaresmallchangesinDNAthatcanhappenwhenacelldividesinanattempttocopyitself. Thesesmallchangescaninfluenceaperson'sphysicalappearanceorcontrolaperson'sabilitytofightadisease.
Thenewly-discoveredmutationsshowthatidenticaltwinsdohavegeneticdifferences, theresearcherssaid. TheresultswererecentlypublishedinNatureGenetics.
Onaverage, identicaltwinshave 5.2 oftheseearlygeneticdifferences, theresearchersfound. Butabout 15 percentofidenticaltwinpairshavemorethanthat. Somemighthaveasmanyas 100 geneticdifferences, Stefanssonsaid.
Thesedifferencesrepresentasmallpartofeachtwin'sgeneticmaterial. Buttheycouldinfluencewhyonetwinistallerorwhyoneisatgreaterriskforsomecancersthantheother.
Inthepast, manyresearchersbelievedphysicaldifferencesseeninidenticaltwinswererelatedmostlytoenvironmentalinfluences, suchasnutritionorlifestylebehaviors.
JanDumanskiisageneticistatSweden'sUppsalaUniversity. Hewasnotinvolvedinthestudy. Hepraisedthefindingsas "aclearandimportantcontribution" tomedicalresearch.
"Theimplicationisthatwehavetobeverycarefulwhenweareusingtwinsasamodel" forexaminingtheinfluencesofgeneticsortheenvironment, Dumanskisaid.
A 2008 paperinTheAmericanJournalofHumanGeneticsfoundsomegeneticdifferencesbetweenidenticaltwins. Thenewstudy, however, goesbeyondearlierworkbyincludingtheDNAofparents, children, husbandsandwivesofidenticaltwins.
Studyingfamilymemberspermittedtheresearcherstoexaminewhengeneticmutationshappenedintwodifferentkindsofcells: thosepresentinonlyoneindividualandthosepassedontotheperson'schildren.
Stefanssonsaidhisteamfoundtwinswhereamutationispresentinallcellsofthebodyofonetwin, butnotintheothertwinatall. However, "sometimesthesecondtwinmayshowthemutationinsomecells, butnotallcells," headded.
Theresearcherssaidtheyalsofoundmutationsthatcameaboutbeforethedevelopingembryosplitintwo.
NancySegalisapsychologistwhostudiestwinsatCaliforniaStateUniversity, Fullerton. Shewasnotinvolvedinthestudy. Butshecalledtheresults "heroicandreallysignificant."
Segaladdedthattheresearchislikelytopersuademorescientiststorethinktheinfluencesofgeneticsandenvironmentontwins. "Twinsareveryalike, butitisnotaperfectsimilarity," shesaid.
I'mBryanLynn.