Imibuzo Eyisibonelo Exoxa Ngemodeli Yamamolekyuli e-DNA nguWatson noCrick
Ngo-1953, uJames D. Watson noFrancis H.C. Crick bavusa ugqozi emhlabeni wesayensi ngokunyathelisa kwabo isakhiwo sama-molecule se-DNA. Lokhu kwembulwa kwesakhiwo se-double helix kwanikeza isisekelo sokuqonda izindlela zofuzo futhi kwavula indlela yentuthuko emangalisayo kwezakhi zofuzo zanamuhla. Leli phepha lizohlola izibonelo ezihlobene nemodeli ehlongozwayo kaWatson noCrick ye-molecule ye-DNA futhi lixoxe ngemiphumela yayo ku-biology yama-molecule kanye nobuchwepheshe bezakhi zofuzo.
Isingeniso ku-DNA
I-DNA, noma i-deoxyribonucleic acid, iyi-molecule egcina ulwazi lwezakhi zofuzo emaseli azo zonke izinto eziphilayo, okuhlanganisa nabantu. Empeleni, i-DNA ihlanganiswa ibe yi-polymer ibe yizintambo ezinde ezakhiwe ngamayunithi aziwa ngokuthi ama-nucleotide. I-nucleotide ngayinye inezingxenye ezintathu: iqembu le-phosphate, ushukela we-deoxyribose, kanye nesinye sezisekelo ezine ze-nitrogen ezihlukene—i-adenine (A), i-thymine (T), i-guanine (G), kanye ne-cytosine (C).
Imodeli kaWatson noCrick ye-Double Helix
UWatson noCrick basikisela ukuthi i-DNA yakhiwe imicu emibili ye-polynucleotide eyakha isakhiwo se-double helix. Le micu ihamba ngezindlela eziphambene (i-antiparallel) futhi ixhunywe ngama-base pair phakathi kwe-adenine ne-thymine, naphakathi kwe-guanine ne-cytosine. Lezi zisekelo zixhunywe ngama-hydrogen bonds: ama-hydrogen bonds amabili axhumanisa u-A no-T, kanti ama-hydrogen bonds amathathu axhumanisa u-G no-C. Lobu budlelwano bokuxhumanisa isisekelo buchaza umthetho kaChargaff, othi inombolo ye-A ku-DNA izolingana nenombolo ye-T kanti inombolo ye-G izolingana nenombolo ye-C.
Imibuzo Nezingxoxo Eziyisibonelo
Umbuzo 1: Yiziphi izingxenye eziyinhloko ze-DNA futhi ukulandelana kwama-base pairs kungawuthinta kanjani umsebenzi wezakhi zofuzo?
Ingxoxo: Izingxenye eziyinhloko ze-DNA yi-nucleotide, equkethe ushukela we-deoxyribose, iqembu le-phosphate, kanye nezisekelo ezine ze-nitrogen: i-adenine (A), i-thymine (T), i-guanine (G), kanye ne-cytosine (C). Ukulandelana okuthile kwalezi zibhangqa zesisekelo kwakha i-gene, okuyisigaba se-DNA esibhala ikhodi ye-protein noma i-RNA molecule enomsebenzi othize. Ukwehluka kokulandelana kwesisekelo kuvumela ukuhlukahluka kolwazi lwezakhi zofuzo olubalulekile emisebenzini ehlukene yezinto eziphilayo. Isibonelo, ukuguqulwa kwezakhi zofuzo noma izinguquko kulandelelwano lwesisekelo ku-gene kungabangela ukuphazamiseka komsebenzi we-protein futhi kubangele izifo zezakhi zofuzo.
Umbuzo 2: Chaza ukuthi ukuhlanganiswa kwesisekelo okuhambisanayo kuqinisekisa kanjani ukuphindaphindwa kwe-DNA okuthembekile.
Ingxoxo: Ukuhlanganiswa kwesisekelo okuhambisanayo phakathi kwe-AT ne-GC kuqinisekisa ukuthi umucu ngamunye we-DNA ungasebenza njengethempulethi yokwenziwa komucu ohambisanayo ngesikhathi sokuphindaphindwa. I-enzyme ye-DNA polymerase ifunda ukulandelana kwesisekelo kumucu wethempulethi futhi inezela ama-nucleotide ahambisanayo kumucu osanda kuhlanganiswa. Isibonelo, uma umucu wethempulethi une-AGCT elandelanayo, umucu ohambisanayo osanda kuhlanganiswa uzoba ne-TCGA elandelanayo. Le nqubo ibalulekile ekuphindaphindweni kwe-DNA okunembile ukuze iseli ngalinye lendodakazi lithole ulwazi olufanayo lwezakhi zofuzo oluvela kuseli lomzali.
Umbuzo 3: Izinto ezitholwe nguWatson noCrick zawuthinta kanjani umkhakha we-biotechnology?
Ingxoxo: Ukutholwa kukaWatson noCrick kwesakhiwo se-DNA esine-helix ephindwe kabili kwaphawula ukuqala kwenguquko kwezobuchwepheshe be-biotechnology. Umphumela owodwa obalulekile kwaba ukuthuthukiswa kwamasu obunjiniyela bezakhi zofuzo, okuhlanganisa ubuchwepheshe be-DNA ephindaphindayo, okuvumela ukufakwa, ukususwa, noma ukuguqulwa kwezakhi zofuzo ezithile. Lokhu kuholele ekusetshenzisweni okuningi okusebenzayo, njengokuthuthukiswa kwezitshalo eziguqulwe izakhi zofuzo ezimelana kakhulu nezinambuzane, ukukhiqizwa kwe-insulin ephindaphindayo yokwelapha isifo sikashukela, kanye nokwelashwa kwezakhi zofuzo ukwelapha izifo zofuzo. Ngaphezu kwalokho, ulwazi ngesakhiwo nomsebenzi we-DNA nalo luye lwaba negalelo ekuthuthukisweni kwamasu okuthola nokuxilongwa kwezifo okunembe kakhudlwana ngephrojekthi yezakhi zofuzo zabantu.
Isiphetho
Imodeli ye-DNA yama-molecule kaWatson noCrick ayichazanga nje kuphela izindlela eziyisisekelo zofuzo kodwa futhi yavula amathuba amasha ocwaningo lwesayensi kanye nezinhlelo zokusebenza ze-biotechnology ezithuthukisiwe. Lokhu kuqonda kusisiza siqonde ukuthi ulwazi lwezakhi zofuzo lukhiqizwa kanjani, ludluliselwa kanjani, futhi ludluliselwa kanjani kusuka kwesinye isizukulwane kuya kwesinye, kanye nokuthi ukuguqulwa ezingeni lama-molecule kungathinta kanjani umzimba wonke. Ngobuchwepheshe, le ntuthuko ibe negalelo emisha eminingi yezokwelapha nezolimo eye yaba nomthelela omuhle empilweni yabantu.
Ekuphetheni le ngxoxo, kusobala ukuthi ukutholakala kukaWatson noCrick kwesakhiwo se-DNA kwakungaphezu nje kwempumelelo emkhakheni we-molecular biology; kwakuyindlela eya enkathini ye-biotechnology eqhubeka nokunikeza amathuba amaningi okuthuthuka kwesayensi kanye nokuthuthukiswa kwekhwalithi yokuphila.
