Wannan lamari na farko na magudin kwayoyin halitta a cikin kadangaru ya haifar da samfurin halitta wanda zai iya taimakawa wajen samun ƙarin fahimtar juyin halitta da ci gaba.
CRISPR-Cas9 ko kuma kawai CRISPR kayan aiki ne na musamman, mai sauri kuma mai araha wanda ke ba da damar gyara kwayar halitta ta hanyar gogewa, ƙarawa ko canza DNA . Acronym na CRISPR yana nufin 'Clustered Regularly Inter-Spaced Palindromic Repeats'. Wannan kayan aiki yana da sauƙi kuma ya fi daidaito fiye da hanyoyin da aka yi amfani da su a baya don gyara DNA.
Kayan aikin CRISPR-Cas9 yana allurar ƙwayoyin halitta a matakin zygote (ƙwayar halitta ɗaya) tare da tsarin DNA da aka yi da (a) enzyme na Cas9 wanda ke aiki a matsayin 'almakashi' kuma yana iya yanke ko share wani ɓangare na DNA, (b) yana jagorantar RNA - jerin da ya dace da kwayar halittar da aka nufa kuma don haka yana jagorantar enzyme na Cas9 zuwa wurin da aka nufa. Da zarar an yanke wani ɓangaren DNA da aka nufa, injinan gyaran DNA na tantanin halitta za su sake haɗuwa da sauran zaren kuma, a cikin wannan tsari, su rufe kwayar halittar da aka nufa. Ko kuma ana iya 'gyara' kwayar halittar ta amfani da sabon samfurin DNA da aka gyara a cikin wani tsari da ake kira gyaran homology directed. Don haka, kayan aikin CRISPR-Cas9 yana ba da damar gyare-gyaren kwayoyin halitta ta hanyar allurar mafita na gyaran kwayoyin halitta a cikin ƙwai mai tarawa guda ɗaya. Wannan tsari yana haifar da canjin kwayoyin halitta (maye gurbi) a cikin duk ƙwayoyin halitta masu zuwa waɗanda aka samar don haka yana shafar aikin kwayar halitta.
Kodayake ana amfani da Cruspr-Cas9 a cikin wani nau'in halitta da yawa gami da kifi, tsuntsaye da dabbobi, zuwa yanzu bai yi nasara ba cikin tsarin halittar halittar halittar dabbobi. Wannan shi ne da farko saboda shinge biyu. Na farko, dabbobi masu rarrafe na mata suna adana maniyyi na dogon lokaci a cikin oviduct nasu yana da wahala a tantance ainihin lokacin hadi. Na biyu, ilimin halittar qwai na dabbobi masu rarrafe yana da fasali da yawa kamar bawoyin kwai, raunin da ba shi da sarari a ciki yana sa ya zama ƙalubale wajen sarrafa amfrayo ba tare da haifar da tsagewa ko lalacewa ba.
A cikin wani labarin da aka ɗora a kan bioRxiv a ranar 31 ga Maris, 2019, masu bincike sun ba da rahoton ci gaba da gwaji na hanyar amfani da gyaran kwayoyin halitta na CRISPR-Cas9 a cikin dabbobi masu rarrafe a karon farko. Nau'in dabbobi masu rarrafe da aka zaɓa a cikin binciken shine ƙadangare mai zafi da ake kira Anolis sagrei ko anole mai launin ruwan kasa wanda ya yaɗu a cikin Caribbean. An tattara ƙadangare a cikin binciken daga wani yanki na daji a Florida, Amurka. Wannan nau'in ya fi dacewa da binciken saboda ƙaramin girmansa, tsawon lokacin kiwo da ɗan gajeren lokaci tsakanin tsararraki biyu.
Don shawo kan gazawar da ake fuskanta a halin yanzu tare da dabbobi masu rarrafe, masu bincike sun yi microinjected abubuwan CRISPR zuwa cikin ƙwai marasa girma yayin da ƙwai ke cikin ovaries na mata kafin hadi. Sun yi niyya ga kwayoyin halittar tyrosinase wanda ke samar da wani enzyme mai sarrafa launin fata a cikin kadangaru kuma idan an cire wannan kwayar halitta za a haifi kadangare a matsayin zabiya. Wannan bayyanannen phenotype na pigmentation shine dalilin zabar kwayar halittar tyrosinase. Ƙwayoyin da aka yi musu allura sai su girma a cikin mace kuma daga baya a haɗe su ta hanyar dabi'a tare da wani namiji ko maniyi da aka adana.
Sakamakon haka, an haifi ƙananan karnuka huɗu masu launin zabiya 'yan makonni kaɗan bayan haka, waɗanda suka tabbatar da cewa an kashe kwayar halittar tyrosinase kuma tsarin gyaran kwayar halittar ya yi nasara. Tunda zuriyar ta ƙunshi kwayar halittar da aka gyara daga iyayen biyu, a bayyane yake cewa abubuwan CRISPR sun daɗe suna aiki a cikin ƙwayar halittar uwa da ba ta girma ba kuma bayan hadi, ta canza kwayoyin halittar uba. Don haka, ƙananan karnuka masu launin zabiya masu canzawa sun nuna cewa an sarrafa tyrosinase a cikin kwayoyin halittar da aka gada daga uwa da uba saboda albinism siffa ce da aka gada daga iyaye biyu.
Wannan shine karo na farko da aka taba yin nazari don samar da ingantaccen halittu masu rarrafe. Binciken na iya yin aiki ta irin wannan hanya a cikin wasu nau'in kadangaru kamar macizai waɗanda hanyoyin yanzu ba su yi nasara ba. Wannan aikin zai iya taimakawa wajen samun ƙarin fahimtar juyin halitta da ci gaba.
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Source (s)
Rasys AM da sauransu. 2019. Bugawa ta Gaba. Gyaran Halittar CRISPR-Cas9 a cikin Lizards Ta hanyar allurar ƙwayoyin halitta marasa takin zamani. bioRxiv. https://doi.org/10.1101/591446
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