Njengoba kunikezwe isigaba esilandelayo esiphathelene nokulawulwa kwezakhi zofuzo, ayini ama - operon futhi atholakala kuphi?
Context:Ukulawulwa kokubonakaliswa kwezakhi zofuzo yizici zemvelo futhi phakathi nezigaba ezahlukahlukene zokuthuthuka kungenzeka esigabeni ngasinye senqubo efana nokubhalwa, ukuhlanganiswa kwe-RNA, ukuhumusha, nokuguqulwa kwe-post-translational kweprotheni. Ukubonakaliswa kwezakhi zofuzo kungathonywa ukulawulwa okuhle noma okungekuhle, kuye ngokuthi yiziphi izinhlobo ezimbili zamaprotheni alawulayo abizwa ngokuthi ama-transcription factors abopha ukulandelana kwe-DNA eduze noma endaweni yokukhuthaza. Iqoqo lezakhi zofuzo ezinomgqugquzeli ofanayo libizwa ngokuthi i - operon, elitholakala ikakhulukazi kuma - prokaryotes nakuma - eukaryotes aphansi (isib., i - Caenorhabditis elegans). Ekulawuleni okuhle kwe-gene expression, i-activator iyisici sokubhalisa esikhuthaza ukubhalwa kabusha lapho sibopha ukulandelana eduze noma ku-promoter. Ukulungiswa okungekuhle kwenzeka lapho esinye isici sokubhalwa esibizwa ngokuthi i-repressor sibopha ukulandelana kwe-DNA okubizwa ngokuthi i-operator, okuyingxenye ye-operon, ukuvimbela ukukopishwa. Ama-repressor angavimbela izakhi ezibizwa ngokuthi ama-inducer (isib., i-allolactose), ngaleyo ndlela avumele ukubhalwa. Amangqamuzana akhethekile angavulwa ama-inducer abizwa ngokuthi ama-inductible genes, ngokungafani nama-constitutive genes acishe asebenze njalo. Ngokuphambene nalokhu kokubili, izakhi zofuzo ezakha izakhiwo zifaka amaprotheni angahlanganyeli ekulawuleni izakhi zofuzo. Ngaphezu kwezenzakalo zokulawula ezihilela i-promoter, ukubonakaliswa kwezakhi zofuzo nakho kungalawulwa yizinguquko ze-epigenetic ku-chromatin, okuyinkimbinkimbi ye-DNA namaprotheni atholakala kumaseli e-eukaryotic.
Ama-operon ayizixuku zezakhi zofuzo ezihlanganyela umshayeli ofanayo. Zitholakala ikakhulukazi kuma-prokaryotes nakuma-eukaryotes aphansi njenge-Caenorhabditis elegans.