Uyini reduplication ye-DNA? Inqubo ye-DNA ukufanisana

Molecule ye-DNA - itholakala chromosome isakhiwo. Omunye chromosome iqukethe molecule elilodwa ehlanganisa imicu emibili. Reduplication ye-DNA - kuyinto ukudluliswa kolwazi ngemva self-ukukhiqizwa kabusha sendikimba komunye-molecule kwenye. Kuyinto esivela kokubili i-DNA ne-RNA. Lesi sihloko sixoxa DNA igceke inqubo.

Imininingwane kawonkewonke futhi izinhlobo DNA zamagama

Kuyaziwa ukuthi ntambo ezisontekile e-molecule ezaziwayo. Nokho, lapho inqubo DNA ukufanisana iqala, bona dispiralized ke uyagudluka, futhi ikhophi entsha ngalinye kwemiqondo. Lapho beqeda kunama-molecule ezimbili ezifanayo ngokuphelele, ngalinye elikwazi kukhona umzali kanye intambo ingane. Lokhu zamagama libizwa semi olandelanayo. molecule e-DNA sishukumiseleka, kodwa ngesikhathi esifanayo endaweni centromere olulodwa, futhi ekugcineni washintsha kuphela uma lokhu centromere division inqubo iqala.

Enye uhlobo libizwa zamagama reparative. Yena, ngokungafani sangaphambilini, ongakaphathelani yisiphi isigaba cell, kodwa iqala uma kwenzeka ukulimala kwe-DNA. Uma kakhulu nemvelo ezahlukene, iseli egcina ngokufa. Nokho, uma umonakalo wendawo, khona-ke ungakwazi ukubabuyisela. Kuye inkinga ukuthi ibuyiselwe noma ukwehlukanisa ezimbili zingu-DNA ngesikhathi esisodwa. Lokhu, njengoba ibizwa, zamagama unscheduled akuthathi isikhathi eside futhi ayidingi amandla amaningi.
Kodwa uma kukhona reduplication DNA ke wachitha amandla amaningi, impahla, welula ubude iwashi lakhe.
Reduplication ihlukaniswe izinkathi ezintathu:

• Ukuqalwa;
• ukunwebeka;
• ukunqanyulwa.

Ake sicabangele ukulandelana DNA ukufanisana.

Ukuqalwa

Ngo-DNA yomuntu - emashumini ambalwa izigidi base ngazimbili (izilwane selibalelwa engamakhulu ayisishiyagalolunye kuphela). DNA reduplication iqala ezindaweni eziningi iketango ngenxa yezizathu ezilandelayo. Ngesikhathi ku-RNA umbhalo kwenzeka, kodwa synthesis DNA imiswa ezinye izindawo ezikhethiwe. Ngakho-ke, inqubo enjalo ngaphambi isamba elanele ketshezi aqoqana cytoplasm amaseli ukuze asekele isakhi sofuzo Inkulumo nomsebenzi kwamangqamuzana iphukile cha. Ngenxa yalokhu, le nqubo kumele kwenzeke ngokushesha ngangokunokwenzeka. Sakaza ngalesi sikhathi kwenziwe, kanye umbhalo akuyona olwenziwa. Ucwaningo luye lwabonisa ukuthi i-DNA reduplication kwenzeka kanye amaphuzu abayizinkulungwane ezimbalwa - izindawo ezincane nge nucleotide thize. Basuke bajoyine umqalisi amaprotheni ekhethekile, nakho belekelelwa enzyme ye-DNA ukufanisana.

Lesi siqeshana DNA okuyinto kwemiqondo ibizwa ngokuthi replicon. Iqala zisuka futhi luphele lapho enzyme evala ukufanisana. Replicon kuyinto ezizimele, futhi usinikeza yonke inqubo isofthiwe yayo.
Inqubo kungenzeka ukuqala wonke amaphuzu ngesikhathi esisodwa, endaweni ethile iqala ekuqaleni, endaweni ethile - kamuva; Kungathatha indawo eyodwa noma ezimbili okuphambene. I zenzeka ngendlela elandelayo lapho isithombe:

• ukufanisana izimfoloko;
• RNA primer.

ukufanisana ekuphambukeni

Le ngxenye inikeza inqubo lapho ku lokuluhlaza unqamukile kuthiwa bafaka kuyi-DNA deoxyribonucleic kwayo. ngaleyo ndlela plugs yakha iso lokho okubizwa ngomlobokazi ukufanisana. Le nqubo ibizwa lwendulelwe yezenzo:

• ukumkhulula ngokuqondene histones endaweni nucleosome - enzyme ezifana methylation DNA ukufanisana, acetylation, futhi phosphorylation ukukhiqiza zamakhemikhali eziningi kuholele amaprotheni ulahlekelwe ababaphathisiwe omuhle ukuthi kusiza ukukhululwa kwabo;
• despiralization - kuyinto unwinding, okuyilona elidingekayo ukuze kukhululwe okwengeziwe sendikimba;
• baphule hydrogen isibopho phakathi imicu DNA;
• kwehlukana zabo emaceleni ezahlukene engqamuzaneni;
• nenkanuko edlulele ezenzeka besebenzisa SSB amaprotheni.

RNA primer

Synthesis ithwala i-enzyme okuthiwa i-DNA polymerase. Nokho, ukuze uqale ngamandla akhe eyedwa ngeke bakwazi, + ngakho ukwenza ezinye enzyme - the polymerase RNA, olubizwa nangokuthi i-RNA kwenziwa. Basuke kuhlelwe imicu okucishe kufane nalokhu deoxyribonucleic ku isimiso complementarity. Ngakho, emizameni RNA zamagama imikhawulo ezimbili, kwenziwa emibili asebesishiyile kuklebhukile imicu DNA.

ukunwebeka

Le nkathi iqale kusukela nucleotide kwalokho futhi 3 'ekupheleni RNA-primer, ethwala i-sekushiwo DNA polymerase. It inamathela lesibili, nucleotide lwesithathu, nokunye. New base ngentambo uxhumeke kwi-chain umzali nge-hydrogen izibopho. Kukholakala ukuthi kwezici ntambo uku 5 '- 3'.
Lapho kwenzeka ohlangothini ekuphambukeni ukufanisana, synthesis senzeka ngokuqhubekayo futhi ngesikhathi esifanayo ibe yinde. Ngakho-ke, kulolu chungechunge ubizwa ngokuthi ehola noma ehola. Yena RNA primer ayisaxhunyanisiwe kwakhiwa.

Nokho, phezu Strand okuphambene umzali nucleotide DNA uqhubeke ukuze ujoyine primer RNA, futhi uchungechunge deoxyribonucleic is kuhlelwe umqondo kolunye uhlangothi kusukela ekuphambukeni ukufanisana. Kulokhu, ibizwa ngokuthi imisiwe noma okusalele emuva.

On the Strand okusalele emuva zamagama kwenzeka yizicucu, lapho omunye ekupheleni ingxenye zamagama iqala kwenye indawo eduze ekusebenziseni ukuthi efanayo RNA primer. Ngakho, kukhona ezimbili imisiwe uchungechunge isinqamu zihlangene DNA ne-RNA. Zibizwa ngokuthi Okazaki izinsalela.

Khona-ke konke iyaphindwa. Khona-ke spliced elinye ijika we Helix, i-hydrogen wavele zokuxhumana zangaphandle emaceleni, okuholela uchungechunge yinde ngesikhathi okusalele emuva kwemiqondo elandelayo isinqamu RNA primer whereupon - Okazaki isinqamu. Ngemva kwalokho, ngesikhathi i-RNA imisiwe-Strand kwenziwa ubhubhe izingcezwana DNA zihlangene zibe munye. Ngakho lesi sifunda senzeka ngesikhathi esifanayo:

• kumiswa entsha RNA primer;
• synthesis Okazaki izingcezwana;
• ukubhujiswa RNA kwenziwa;
• babuyelana ibe wesifunda olulodwa.

Ukunqanyulwa

Inqubo uyaqhubeka njengoba nje ezimbili angahlangabezani ekuphambukeni ukufanisana, noma omunye wabo ekupheleni kwe-molecule ukuza. Nakuphela imihlangano, izimfoloko DNA indodakazi imicu zihlangene ngu enzyme. Kuleli cala, uma i-plug idluliswa ngasekupheleni engqamuzaneni, DNA reduplication ekugcineni usebenzisa enzyme akhethekile.

ukulungiswa

Kule nqubo, indima ebalulekile inikezwa control (noma ukulungiswa) ka ukufanisana. Ukuze ubeke zamagama uthola zonke izinhlobo ezine ama-nucleotide, futhi probe ngu ukubhanqa DNA polymerase ukhetha lezo kudingeka.

I nucleotide wayefisa babe sebakwati hydrogen izibopho kanye nucleotide efanayo phezu Strand isifanekiso DNA. Ngaphezu kwalokho, phakathi umgogodla sugar-phosphate kumele babe ibanga elithile njalo elihambisana izindandatho amathathu lezisekelo ezimbili. Uma nucleotide akusho nalezi zimfuneko, uxhumano ngeke kwenzeke.
Control Kwenziwa ngaphambi kokuba lithathwa wesifunda futhi ngaphambi kokuba uvule nucleotide okwalandela. Ngemva kwalokho, ukuxhumana saharofosfata backbone.

kokuhlukana mutational

Mshini ye-DNA ukufanisana, naphezu iphesenti eliphakeme lokunemba uhlale yokuphazamiseka kwayo, ababiziweyo ikakhulukazi "zofuzo." Cishe abantu abangaba yizinkulungwane base ngazimbili, kukhona iphutha elilodwa ukuthi konvariantnaya ngokuthi reduplication.

Kwenzeka ngenxa yezizathu ezahlukene. Ngokwesibonelo, at lokuhlala eliphezulu kakhulu noma eliphansi kakhulu we-nucleotide deamination ka-cytosine, khona mutagens ku zamagama kokubili. Kwezinye izimo, iphutha kungenziwa wakhuzwa ukulungisa izinqubo kwezinye ukulungiswa, kusuka kube nzima.

Uma umonakalo abathintekayo isikhala ubuthongo, iphutha ngeke kube nemiphumela emibi kakhulu lapho umuntu kukhona DNA ukufanisana inqubo. Nucleotide ukulandelana isakhi singenzeka yisiphambeko kokuzalela. Khona-ke akunjalo, futhi yalokho emibi kungaba sengathi ukufa iseli, kanye nokufa kwalo lonke umzimba. Kufanele kukhunjulwe ukuthi zofuzo zisekelwe kokuhlukana mutational, okwenza pool isakhi sofuzo ka plasticity.

methylation

Ngesikhathi zamagama, noma ngokushesha ngemuva kokuba kwenzeke methylation ngamaketanga. Kukholakala ukuthi le nqubo kuyadingeka ukuze umuntu akha Ama-chromosomes e nokulawula isakhi sofuzo umbhalo. Kule nqubo bacterium DNA ukhonza Ukuvikelwa baso engibukhulumile ukusika enzyme.