Ulwakhiwo lweDNA kunye nesakhiwo seRNA

Ukuba ucinga ukubonakala kwe- molecule ye- DNA, ngoko kufana nokuhamba okuphosakeleyo, okwakhiwa ngamaketanga amabini e-polynucleotide, aphikisana kunye kunye kunye ne-axis eyodwa.

Njengomgaqo, isakhiwo se-DNA sinokuqwalaselwa kwisikhokelo sohlalutyo lwenkqubo, ngelixa enye eyona nto imiselwe ngokuqinileyo (ngokuqhelekileyo karhulumente) ukulungiswa kwe-deoxyribonucleoside monophosphates-dNMP, eyenza izikhonkwane ze-polynucleotide.

Kwi-cell engatshintshiyo, i-mononucleotide idibene ne-phosphodiester izibophelelo, ngelixa iziphelo ze-polynucleotide chain zinezinto ezihlukeneyo zelungiselelo lamaqela angempela: iqela le-phosphate lisekupheleni kwesi-5, kwaye i-OH iqela ekupheleni kwe-3.

Ukuba sicinga i-molecule equlethwe ngamaketanga amabini, ngoko isakhiwo se-DNA siya kuba njalo ukuba i-polynucleotide ietyunyuke ibe yinto ephikisanayo. Kule meko, iinqetyambo, kwisakhiwo esinjalo, ziya kugcinwa ngenxa yezibophelelo ze-hydrogen ezikhoyo phakathi kweziseko ze-A-T kunye ne-GC, zilele kwindiza efanayo kunye ne-axis ephezulu ye-molecule ye-helix. Lezo zintsebenziswano zama-hydrophobic ezenza phakathi kweziseko zelo molecule ziqinisekisa ukuzinza kwe-double helix. Kulo hlobo lwe- molecule, isakhiwo se- DNA sibonakaliswe ukuhlanganiswa kwamaketanga e-polynucleotide, kodwa kungekhona ukuba yiyiphi, kuba i-nucleotide yayo iyahluka.

Ukongezelela, ucinga ukuba yintoni isakhiwo se-DNA, kufuneka sikhankanywe ukuba i-molecule ngayinye "iipakethe" ngokwayo, ikhethekileyo ichromosome. Ezi i-chromosomes ziqulethe iintlobo zeeprotheni ezihambelana nokulandelelana ngokucacileyo kwesakhiwo se-molecule ye-DNA. Ezi proteins zihlelwa kwiindidi ezi-2: iimbali ze-histones kunye ne-non-histone proteins. Kwinkimbinkimbi nge-DNA yenyukliya yeeseli, ezi proteyini zibizwa ngokuba yi-chromatin.

Ukubonakalisa isakhiwo se-DNA, kufuneka kukhonjiswe ukuba i-chromatin ineentlobo ezintlanu ze-histones, into edibeneyo edibeneyo, eyenza i-histones kunye noxhumano olunamandla kunye ne-DNA. Ubunzima be-histones kunye nommandla othile we-molecule ye-DNA, equle iindidi ezili-146 ze-nucleotide, ezidibeneyo, ezibangele ukubunjwa kwama-nucleosomes.

Ama-molecule e-DNA afaka isakhiwo se-DNA ayilona i-histones, ziintlobo ezahlukeneyo zeeprotheni ezilawulayo ezinxulumene neendlela ezithile zeDNA. Kwakhona, isakhiwo se-molecule ye-DNA sincediswa ngama-enzymes anika i-biosynthesis.

Ukufunda isakhiwo se-DNA kunye ne-RNA kwisakhelo sohlalutyo lwenkqubo lulandela kuphela kwisakhiwo esiyinkimbinkimbi, oko kukuthi, xa sicinga isakhiwo se-DNA, kubalulekile ukuqwalasela isakhiwo se-RNA.

Isakhiwo saso esiyintloko, kunye nakwimeko ye-molecule ye-DNA, yindlela yokuguqula i-ribonucleoside monophosphates, kwaye kufuneka kuqatshelwe ukuba, ngokungafani ne-molecule ye-DNA, zonke iindidi ze-RNA zinomnye umgca we-polynucleotide. Ngokwakheko lwe-molecule ye-RNA, iintambo zalo zizenza i-"pinpins "ezinokuthi zenze i-loops eziphambili ezidalwe yiziseko ze-AU kunye ne-GC kwaye zizinzile ngenxa yezibophelelo ze-hydrogen.

Njengomthetho, i-molecule yesilinganiso se-DNA iquka malunga neebini ezizigidi ezili-150 ze-nucleotide, kwaye ubude bayo buyi-centimitha. Kuhlalutyo lwebhubhoratri, iimolekyuli ezinjalo ziphazamisekile kakhulu uphando, kuba xa zisuswe kwiisuncu, i-molecule ihlala ihluke kakhulu kwaye ibe yincinci encinane. Ukuphelisa oku kuphazamiseka, indlela ye-PCR isetyenziswe kwizifundo - impendulo ye-polymerase chain, ngaphakathi kwesikhokelo sokukhetha okukhethiweyo kwamacandelo ngamnye e-molecule ye-DNA eyenzekayo kwaye iinqununu eziyimfuneko ekufundwayo zifunyenwe.