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AncientDNAandGeneticEngineering
andeliminateinvadinggeneticmaterialżPalindromicrepeatswereinitially
discoveredinthe1980sinE.coli(Ishinoetalż,1987),buttheirfunctionwasnot
confrmeduntil2007byBarrangouandcolleagues,whodemonstratedthat
S.thermophiluscanacquireresistanceagainstabacteriophagebyintegrat-
ingagenomefragmentofaninfectingvirusintoitsCRISPRlocus(Barran-
gouetalż,2007)żThreetypesofCRISPRmechanismshavebeenidentifed,
ofwhichtypeIIismoststudiedżInthiscase,invadingDNAfromvirusesor
plasmidsiscutintosmallfragmentsandincorporatedintoaCRISPRlocus
amidstaseriesofshortrepeats-around20basepairs(bp)żThelociare
transcribedandtranscriptsarethenprocessedtogeneratesmallRNAs
(crRNA-CRISPRRNA),whichareusedtoguideendonucleasestothecom-
plementarysequenceswithininvadingDNAż
UsingtheCRISPR-Castechnique,onecanpreciselydestroythetarget
geneorchangethemutatedgeneintothewildtypeoneżItisexpected
thatthetechniquewillbeusedtourepair”genesresponsibleforhereditary
diseases;however,therearemanyscientistsclaimingthatthetechniqueis
yetnotonehundredpercentsafeandcouldleadtounwantedsideefectsż
Despitethat,agroupofChinesescientistsundertookthefrsttrialsandin-
jectedapersonwithcellsthatcontaineditedgenesżTheybelievedthat
geneeditingcouldimprovetheabilityofimmunecellstoattackcancerż
AteamledbyoncologistLuYouatSichuanUniversityinChengdudelivered
themodifedcellsintoapatientwithaggressivelungcancerattheWest
ChinaHospital(Liangetalż,2015)żTheresearchersremovedimmunecells
fromtherecipient’sbloodandthendisruptedthegenecodingforthe
proteinPD-1,whichnormallyputsthebrakesonacell’simmuneresponse:
cancerstakeadvantageofthatfunctiontoproliferateżTheeditedcellswere
culturedtoincreasetheirnumberandinjectedbackintothepatientżThe
hopewasthat,withoutPD-1,theeditedcellswouldattackanddefeat
thecancerżThereareplanstousethesametechnique,inbothChinaand
theUS,fortreatmentofpatientswithothertypesofcancer(Cyranoski,
2016)ż
ExceptforapplicationsofthenewtechniquesofDNAanalysisinmed-
icine,theyhavebeenaveryimportanttoolforstudyingevolutionofliving
organismsżThediscoverythatDNAsurvivesinancientplantoranimalre-
mainsandcanbeamplifiedbythepolymerasechainreactionand
sequencedhasgreatlyafectedstudiesonevolutionżThefrstpublished
