I-molecule ye-DNA: amanqanaba ombutho wendalo

I-molecule ye-DNA yi-polynucleotide eneeyunithi ze-monomer ezine ezine-deoxyribonucleotide (i-damp, i-DGMP, i-DCMF kunye ne-DTMP). Ubudlelwane kunye nokulandelelana kwezi nucleotides kwi-DNA yezinto eziphilayo ezahlukeneyo. Ukongeza kwiziseko eziphambili ze-nitrogen, kukho ezinye i-deoxyribonucleotide kwi-DNA eneziseko ezincinane: 5-methylcytosine, 5-hydroxymethylcytosine, 6-methylaminopurine.

Emva kokusebenzisa indlela ye-X-ray crystallography yokufunda i-macromolecules yezinto eziphilayo kunye nokufumana iipatheni ze-X-ray ezigqibeleleyo, kwakunokwenzeka ukucacisa isakhiwo se-molecular DNA. Le ndlela isekelwe kwinto yokuba isigxina se-X-rays isiganeko kwi-cluster yamaqoqo e-atom senza umzekelo we-diffraction, oxhomekeke ngokukodwa kwi-atomic ubunzima bala ma-athomu, indawo yawo kwindawo. Kwiminyaka engama-40 yekhulu lokugqibela, inkolelo yayiqhubekile malunga nesakhiwo sesithathu se-molecule ye-DNA. U.A. Astbury wabonisa ukuba i- deoxyribonucleic acid iyimodeli ye-nucleotides ephezulu.

Isakhiwo esona sikhulu se-DNA

Isakhiwo esiyintloko se- nucleic acid sisetyenziselwa ukulandelelaniswa kwamalungiselelo e-nucleotides kwi-DNA ye-polynucleotide. I-nucleotides zidibaniswa kunye nezibophelelo ze-phosphodiester ezakhiweyo phakathi kweqela le-OH kwindawo ye-5 ye-deoxyribose ye-nucleotide enye kunye ne-OH iqela kwi-3 isikhundla se-pentose enye.

Iipropati ze-biological ze-nucleic acids zixhomekeke ngobuhlobo bolunga kunye nokulandelelana kwee-nucleotides kunye neketoni ye-polynucleotide.

Ukubunjwa kwe-nucleotide ye-DNA kwiindawo ezahlukeneyo zeeronomic amaqela ngokucacileyo kwaye kuqinisekiswa ngumlinganiselo (Г + Ц) / (А + Т). Ukusebenzisa umbandela othile, iqondo lobunzima be-nucleotide yokwakhiwa kweDNA kwimvelaphi eyahlukileyo. Ngaloo ndlela, kwizityalo eziphezulu kunye nezilwanyana, umlinganiselo (T + U) / (A + T) uhlukahluka kwaye unenani elingaphezulu kwe-1. Iimpawu ezincinci, ubuncinci be-coefficient bubanzi phakathi kwe-0.35 ukuya ku-2.70. Ngexesha elifanayo, iindili ze-somatic zeentlobo ze-biological ziqukethe i-DNA ye-nucleotide yokwakhiwa, oko kukuthi, umntu unokuthi i-DNA yezinye iintlobo zifana nomxholo wee-HS zombini.

Ukuqulunqwa kobunzima be-DNA nucleotide ukwakheka ngumbono olinganayo awunikezeli ulwazi kwiimpawu zayo eziphilayo. Okukugqibela kubangelwa ukulandelana kweendawo ezahlukeneyo ze-nucleotide kwi-chain ye-polynucleotide. Oku kuthetha ukuba ulwazi lofuzo kwi-molecule ye-DNA lukhowudiwe ngokulandelelana ngokulandelelanayo kweeyunithi ze-monomeric.

I-molecule ye-DNA iqulethwe ngokulandelelana kwe-nucleotide eyenzelwe ukuqaliswa nokupheliswa kwe- DNA synthesis (replication), i- RNA synthesis (transcription), iprotheni synthesis (translation). Kukho ukulandelelaniswa kwe-nucleotide ekhonza ukubopha imimoleksi elawulayo yokusebenza kunye neyokuvimbela, kunye nokulandelelana kwe-nucleotide engenayo nayiphi na i-genetic information. Kukho neendawo eziguqulwayo ezikhusela i-molecule kwizenzo ze-nucleases.

Inkinga yokulandelelana kwe-nucleotide ye-DNA ayizange isonjululwe ngokuzeleyo ukuya kutsho. Ukunqunywa kwendlela yokuhamba kwe-nucleotide ye-nucleic acids yinkqubo enzima ebandakanya ukusetyenziswa kwendlela yokucoca i-nuclease yee-molecules zibe ngamaqhekeza ahlukeneyo. Kuze kube yimhla, ukulandelelana okupheleleyo kwe-nucleotide yamanzi ase-nitrogen kuye kwasungulwa ezininzi ze-TRNAs ezivela kwimvelaphi eyahlukileyo.

I-molecule yeDNA: isakhiwo sesekondari

UWatson kunye noCrick benza umzekelo we-helix kabini ye-deoxyribonucleic acid. Ngokwale mzekelo, ezimbini iintambo ze-polynucleotide zibophelana, ngaloo ndlela zenza uhlobo oluthile lokuhamba.

Iziseko ze-nitrojeni zazo zifumaneka ngaphakathi kwisakhiwo, kwaye umqolo we-phosphodiester ungaphandle.

I-molecule yeDNA: isakhiwo sezemfundo

I-DNA yomgca kwiselfowine inomlinganiselo weklekyuli ehlangeneyo, ifakwe kwi-compact structure kwaye ithatha kuphela i-1/5 yevolumu yeseli. Umzekelo, ubude be-DNA ye-chromosome yabantu bufikelela ku-8 cm, kwaye bupakishwe ukuze lufike kwi-chromosome ngobude be-5 nm. Ukupakisha kunokwenzeka ngenxa yobuninzi bezakhiwo zeDNA. Kule ndlela kulandela ukuba i-DNA i-DNA ye-double-stranded helix kwisithuba iyakwazi ukuqhubela phambili kwisakhiwo esithile se-tertiary-superhelix. I-Superspiral conformation ye-DNA ibonisa i-chromosomes yezilwanyana eziphezulu. Isakhiwo esinjalo semfundo ephakamileyo sizinzileyo ngokubambisana kunye nama-amino acid asele ayenzela iiprotheni ezenza i-nucleoprotein complex (chromatin). Ngenxa yoko, i-DNA yamaseli e-eukaryotic inxulumene neeprotheni zendalo ezisisiseko-i-histones, kunye nama-proteine acidic kunye ne-phosphoproteins.