Ukuphindaphindwa kwe-DNA
Ukuphindaphinda kwe-DNA kuyinqubo eyisisekelo yezinto eziphilayo evumela amangqamuzana ukuthi aphinde izinto zawo zofuzo ngaphambi kokuhlukana kweseli, ukuze iseli ngalinye lendodakazi lithole ikhophi efanayo ye-DNA. Le nqubo iyisisekelo sefa lezakhi zofuzo futhi idlala indima ebalulekile ekukhuleni, ekulungiseni nasekugcinweni kwezinto eziphilayo. Ukuqonda indlela yokuphindaphinda kwe-DNA akubalulekile nje kuphela kubhayoloji eyisisekelo kodwa futhi kunemiphumela ebanzi emikhakheni efana nezakhi zofuzo, ezokwelapha, kanye ne-biotechnology.
Isakhiwo se-DNA kanye nokubaluleka kokuphindaphinda
I-DNA, noma i-deoxyribonucleic acid, iyi-molecule egcina ulwazi lwezakhi zofuzo emaseli. I-DNA iqukethe imicu emibili ye-polynucleotide eyakha i-double helix. I-nucleotide ngayinye iqukethe iqembu le-phosphate, ushukela we-deoxyribose, kanye nesinye sezisekelo ezine ze-nitrogen: i-adenine (A), i-guanine (G), i-cytosine (C), kanye ne-thymine (T). Lezi zisekelo zihlangana ngqo (A no-T, kanye no-G no-C) ngezibopho ze-hydrogen, zakha "ama-rung" e-double helix ye-DNA.
Ukuphindaphindwa kwe-DNA kumele kwenzeke ngokunemba okukhulu ngoba amaphutha angaholela ekuguqukeni okulimazayo. Ngaphezu kwalokho, ukuphindaphindwa okuphumelelayo kuqinisekisa ukuthi amangqamuzana asanda kwakheka angasebenza kahle, okugcina ubuqotho bezakhi zofuzo zezinto eziphilayo.
Izigaba Zokuphindaphinda kwe-DNA
Ukuphindaphinda kwe-DNA kwenzeka ngochungechunge lwezinyathelo ezihlelekile kakhulu, okubandakanya ama-enzyme namaprotheni amaningi akhethekile.
1. Ukuqaliswa
Inqubo yokuphindaphinda kwe-DNA iqala endaweni ethile ku-molecule ye-DNA ebizwa ngokuthi "umsuka wokuphindaphinda" (ori). Kumabhaktheriya, ngokuvamile kuba ne-ori eyodwa, kuyilapho kuma-eukaryotes, kukhona ama-ori amaningi ukuze kusheshiswe inqubo yokuphindaphinda. I-enzyme ye-helicase iqala inqubo ngokukhulula i-double helix, ihlukanise imicu emibili ye-DNA bese yakha isakhiwo esaziwa ngokuthi "i-replication fork."
Phakathi nalesi sigaba, amaprotheni okubopha izintambo ezinezintambo ezi-single-strand (SSB) azinzisa izintambo ze-DNA ezihlukanisiwe ukuze zingaphinde zihlangane. Okulandelayo, i-enzyme ye-primase ihlanganisa i-primer ye-RNA emfushane enikeza indawo yokuqala ye-DNA polymerase ukuqala ukuhlanganisa intambo entsha ye-DNA.
2. Ukwelula
Uma i-primer isifakiwe, i-enzyme ye-DNA polymerase iqala ukuhlanganisa umucu omusha we-DNA ngokufaka ama-nucleotide kumucu okhulayo, ngokusho kokuhlanganiswa kwesisekelo esithile. I-DNA polymerase inganweba umucu kuphela ohlangothini oluphakathi kuka-5′ no-3′. Ngakho-ke, umucu owodwa, obizwa ngokuthi umucu ohamba phambili, uhlanganiswa njalo ngokulandela isiqondiso sefoloko lokuphindaphinda.
Ngokuphambene nalokho, umucu ophambene, obizwa ngokuthi umucu ohlala isikhathi eside, wenziwa ngokungaqhubeki njengochungechunge lwezingcezu ezimfushane ezibizwa ngokuthi izingcezu ze-Okazaki. Isingcezu ngasinye se-Okazaki siqala nge-RNA primer bese kamuva sihlanganiswa ndawonye ukuze sakhe umucu owodwa oqhubekayo.
3. Ukuqeda
Ekupheleni kokuphindaphindwa, i-RNA primer iyasuswa bese ithathelwa indawo yi-DNA polymerase. Okulandelayo, i-enzyme ligase ijoyina izingcezu ze-Okazaki entanjeni engemuva, ikhiqize intambo ye-DNA eqhubekayo, engashintshi.
Ezintweni eziphilayo ze-eukaryotic, izindawo ezikhethekile ekugcineni kwama-chromosome abizwa ngokuthi ama-telomere nazo ziyaphindaphindwa. Ama-telomere asiza ekuvimbeleni ukulahleka kolwazi olubalulekile lwezakhi zofuzo ngesikhathi sokuphindaphinda, kanti i-enzyme i-telomerase idlala indima ebalulekile ekugcineni ubude be-telomere.
Ama-enzyme namaProtheyini Kubalulekile Ekuphindaphindweni kwe-DNA
Ama-enzyme namaprotheni ahlukahlukene adlala indima ebalulekile ekuphindaphindweni kwe-DNA okuphumelelayo. Nazi ezinye zazo:
1. I-Helicase: Ivula umucu ophindwe kabili we-DNA ngokuphula izibopho ze-hydrogen phakathi kwama-base pairs, yakha ifoloko lokuphindaphinda.
2. I-Primase: Ihlanganisa ama-primer amafushane e-RNA anikeza indawo yokuqala ye-DNA polymerase.
3. I-DNA Polymerase: Ifaka ama-nucleotide ekugcineni kwe-primer noma i-strand ekhulayo, yakha i-strand entsha ye-DNA.
4. I-DNA Ligase: Ixhumanisa izingcezu ze-DNA ezihlukene, ikakhulukazi ekuhlanganiseni izingcezu ze-Okazaki entanjeni engemuva.
5. Iphrotheni Yokubopha I-Single Strand (SSB): Iqinisa imicu ye-DNA evulekile ukuze ingaxhumani kabusha.
6. I-Topoisomerase: Ivimbela ukugoqana ngokweqile kwe-DNA ngokuphula umucu owodwa noma yomibili ye-DNA ukuze ikhulule ukucindezeleka, bese ixhumanisa kabusha.
7. I-Telomerase: Yelula ama-telomere emaphethelweni ama-chromosome kuma-eukaryotes, okubalulekile ekubhekaneni nenkinga yokuphindaphinda kokuphela kwama-chromosome.
Ukunemba Nokulungiswa Kwephutha
Ukuphindaphinda kwe-DNA okunembile kuyisihluthulelo sokugcina ubuqotho bezakhi zofuzo. I-DNA polymerase inekhono lokulungisa elaziwa ngokuthi ukuhlola kabusha. Uma i-DNA polymerase ifaka i-nucleotide engalungile, ingabona lokhu kungafani, inqume ingxenye engalungile, bese iyishintsha nge-nucleotide efanele.
Ngaphezu kwalokho, kunezindlela zokulungisa ngemva kokukopisha ezisingatha amaphutha angafundwa kahle. Lokhu kufaka phakathi ukulungiswa okungafani, okuqaphela futhi kulungise izisekelo ezingasebenzi kahle.
Izicelo kanye Nemiphumela Yokuphindaphinda kwe-DNA
Ukuqonda ukuphindaphindwa kwe-DNA kunezindlela eziningi ezibalulekile. Ku-biotechnology, inqubo ye-Polymerase Chain Reaction (PCR) isebenzisa izimiso zokuphindaphindwa kwe-DNA ukuze kuthuthukiswe izingcezu ezithile ze-DNA ngaphakathi kwe-vitro. Le ndlela ibalulekile ocwaningweni lwezakhi zofuzo, ekuhlolweni kwe-forensics, ekuxilongweni kwezifo, nokuningi.
Kwezokwelapha, ukungasebenzi kahle kokuphindaphindwa kwe-DNA kungaholela ezifweni ezahlukahlukene zofuzo kanye nomdlavuza. Ukuthuthukisa imithi emisha ehlose ama-enzyme athile okuphindaphindwa kumaseli omdlavuza kuyindawo yocwaningo olunzulu.
Isiphetho
Ukuphindaphinda kwe-DNA kuyinqubo ebalulekile eqinisekisa ukuthi iseli ngalinye elisha lithola ikhophi eqondile nephelele ye-DNA yalo. Ukunemba nokusebenza kahle kokuphindaphinda kwe-DNA kugcinwa ngokubambisana okucophelela kwama-enzyme namaprotheni amaningi. Ngokuqonda okujulile kokuphindaphinda kwe-DNA, singaqhubeka nokwandisa ulwazi lwethu lwezakhi zofuzo, sithuthukise amasu e-biotechnology, futhi sithuthukise ukwelashwa okusebenza kahle kakhulu. Njengenye yezinqubo eziyisisekelo kakhulu zebhayoloji, ukuphindaphinda kwe-DNA kuyaqhubeka nokuba yindawo ebalulekile ocwaningweni lwesayensi olukhulayo.
