Molecule ye-DNA: amazinga yenhlangano kwesakhiwo

DNA mpilo - a amayunithi polynucleotide monomer ezine deoxyribonucleotide (dAMF, dGMP, dCMP futhi dTMP). Isilinganiso wokulandelana yalezi nucleotide ku-DNA eziphilayo ezahlukene bangabantu ababili abahlukene. Ngaphandle izisekelo esemqoka ye-nitrogen e-DNA iqukethe ezinye izisekelo ezincane deoxyribonucleotides 5-methylcytosine, 5-oksimetiltsitozin, 6-methylaminopurine.

Kwake kwaba khona kungenzeka ngokusebenzisa indlela ye-X ray crystallography ukufunda macromolecules begazi futhi bathole ephelele ze-X ray, kwakunokwenzeka ukuthola ukwakheka kwama-molecule ye-DNA. indlela wathi isekelwe eqinisweni lapho kwavela khona inhlansi parallel X-ray kwesigameko a crystalline cluster athomu, wakha iphethini umumo womsebenzi, okuyinto ikakhulu incike atomic weight ukuzulazula kwama-athomu, futhi indawo yabo space. Esikhathini 40s kwekhulu elidlule, imfundiso yokuziphendukela isakhiwo ezintathu-ntathu of molecule ye-DNA iye phambili. U. Astbury wafakazela ukuthi deoxyribonucleic acid kuyinto inqwaba esikhulu nucleotide flat.

Isakhiwo eyinhloko molecule ye-DNA

Ngaphansi isakhiwo eyinhloko of acid nucleic, ehloselwe ekulandelaneni nucleotide ku polynucleotide ilungiselelo DNA chain. Nucleotide kuthiwa ahlanganiswa ndawonye yi-phosphodiester izibopho okuyinto akhiwa phakathi iqembu OH ngesikhathi 5 isikhundla esisodwa nucleotide futhi deoxyribose le OH iqembu ku-isikhundla 3 lomunye pentose.

I izakhiwo begazi we nucleic acid isilinganiso kunqunywa qualitative kanye ukulandelana nucleotide yochungechunge polynucleotide.

Ukwakheka nucleotide ye-DNA kusukela eziphilayo bezinhlanga ezahlukene taxonomic sicaciselwe futhi inqunywa isilinganiso (G + C) / (A + T). Ukusebenzisa isici ngokucacile wayezimisele yi-degree of heterogeneity sokuqanjwa nucleotide ye-DNA kusukela eziphilayo Lokudabuka ezahlukene. Ngakho, ngo-izitshalo ephakeme nezilwane isilinganiso (G + C) / (A + T) kuyahlukahluka kancane futhi inenani elikhulu ukwedlula 1. Ukuze nezilwanyana ezincane ngokucacile Coefficient sehluka kakhulu - kusuka 0.35 kuya 2.70. Nokho, amaseli ukuphathwa kwabathintwayo kohlobo of okuqukethwe i-DNA okufanayo nucleotide Ukwakheka, isb. E. Singasho ukuthi okuqukethwe GC ngazimbili elisekela DNA zenye ayafana yini.

Ukunqunywa heterogeneity sokuqanjwa nucleotide ye-DNA ngesilinganiso esingamaphesenti ngokucacile akukuniki ulwazi mayelana impahla yayo begazi. Muva nje, ngenxa ezahlukene othize nucleotide ngekulandzelana izingxenye polynucleotide chain. Lokhu kusho ukuthi ukwaziswa kwezakhi zofuzo okubhalwe molecule e-DNA thize amayunithi yayo monomeric.

A molecule ye-DNA ehlanganisa nucleotide ukulandelanisa senzelwe emizameni kanye nokumiswa izinqubo zamagama ye-DNA (ukufanisana) RNA zamagama (umbhalo) amaprotheni zamagama (translation). Kukhona ukulandelanisa nucleotide ukuthi ukukhonza ukuhlanganisa uxhumano nomsebenzisi Kuvuselela ethize kanye nama-molecule zokulawula inhibitory, kanye nucleotide ukulandelanisa okuyinto ningathwali yiluphi ulwazi zofuzo. Kukhona futhi Ushintshe zasendle, ezikhona ukuvikela amangqamuzana kusukela nucleases.

Inkinga ye ukulandelanisa nucleotide ye-DNA angakafakwa ingaxazululeki ngokuphelele. Ukunqunywa nucleotide ukulandelana acid nucleic kuyinto inqubo isikhathi, esihlinzeka ukusetshenziswa nuclease cleavage indlela molecule ethize ku izingcezwana ehlukile. Kuze kube manje, ephelele nucleotide ukulandelana lezisekelo nitrogen amiselwe iningi tRNA imvelaphi ezahlukene.

Molecule ye-DNA: isakhiwo yesibili

Watson Crick benze i-model of the Helix kabili deoxyribonucleic acid. Ngokulandela le-model, amaketanga omabili polynucleotide entwine nomunye, kanjalo zakha isimiso uhlobo Helix.

lezisekelo nitrogen ukuthi akuphi ngaphakathi isakhiwo, kanye backbone phosphodiester - ngaphandle.

Molecule ye-DNA: isakhiwo ephakeme

I-DNA komugqa kuseli has ukuma i-molecule ye-side, it is zahlanganiswa ngo isakhiwo compact futhi kuthatha kuphela 1/5 of ivolumu cell. Ngokwesibonelo, i-DNA yezakhi womuntu chromosome ubude 8 cm, futhi igcwele ukuze kuyavumelana chromosome nge ubude 5 NM. ukustaka okunjalo kungenzeka ngenxa yokuba khona we Helical izakhiwo DNA. Kule kusobala ukuthi kabili balahleke DNA Helix emkhathini kungaba okunye emakhiyubhi isakhiwo ethile ephakeme - superhelix. conformation Supercoiled izici DNA Ama-chromosomes e eziphilayo ephakeme. isakhiwo esinjalo ephakeme Ukuzinziswa izibopho covalent ukuba acid acid izinsalela ezakha amaprotheni ukuthi zakha eziyinkimbinkimbi nucleoprotein (chromatin). Ngakho-ke, i-DNA lamaseli eukaryotic elihlobene ne amaprotheni uhlamvu ikakhulu eziyisisekelo - histones, kanye amaprotheni esidi fosfoproteidami.