The DNA: amaudindo ya gulu structural

DNA - ndi mayunitsi polynucleotide monomer amene ali anayi deoxyribonucleotide (dAMF, dGMP, dCMP ndi dTMP). The chiŵerengero cha ndondomeko ya nucleotides izi mu DNA ya zinthu zosiyana ndi osiyana. Kuwonjezera pa nitrogenous zapansi chachikulu DNA mulinso zina zapansi zazing'ono deoxyribonucleotides ndi 5-methylcytosine, 5-oksimetiltsitozin, 6-methylaminopurine.

Nthawi ina kunali kuthekera kwa ntchito njira X-ray crystallography kuphunzira macromolecules kwachilengedwenso ndi kupeza wangwiro X-ray, zikanakhala zotheka kuti tipeze kapangidwe maselo a DNA. njira anati zachokera chakuti mtengo wa kufanana X-ray zinachitika pa crystalline limodzi maatomu, ndipamene mapindidwe akuwala chitsanzo, amene makamaka zimadalira kulemera atomiki ya ma atomu, ndi malo awo danga. Mu 40s Mu zaka zapitazo, chiphunzitso cha dongosolo atatu azithunzi omwe tikunena za DNA ayikidwa patsogolo. U. Astbury anatsimikizira kuti deoxyribonucleic acid ndi okwana superimposed nucleotides mosabisa.

Kapangidwe yoyamba ya DNA

Mu dongosolo chachikulu zidulo mkati amatanthauza ndi ndondomeko ya nucleotides mu polynucleotide dongosolo DNA unyolo. Nucleotides umanena limodzi mwa maunyolo phosphodiester amene anapanga pakati pa gulu HA pa 5 udindo wa nyukiliotayidi wina ndi deoxyribose o-gulu udindo 3 pentose wina.

The katundu zamoyo asidi chiŵerengero mkati anatsimikiza mtima Mkhalidwe ndi limodzi nyukiliotayidi ndondomeko ya unyolo polynucleotide.

The nyukiliotayidi zikuchokera DNA kwa zamoyo za magulu osiyana taxonomic lachindunji ndipo watsimikiza ndi chiŵerengero (G + C) / (A + T). Ntchito chinthu kulunjika anatsimikiza ndi mlingo wa heterogeneity wa nyukiliotayidi zikuchokera DNA ku tizilombo chiyambi osiyana. Choncho, zomera apamwamba ndi nyama chiŵerengero (G + C) / (A + T) zimasiyanasiyana pang'ono ndipo ali ndi mtengo wake woposa 1. tizilombo kulunjika koyefishienti zimasiyana - kuchokera 0,35 kuti 2,70. Komabe, maselo somatic kwa nyama ya DNA muli yemweyo nyukiliotayidi zikuchokera, mwachitsanzo. E. tinganene kuti zili GC awiriawiri zapansi wa DNA ya mtundu umodzi zofanana.

Khama la heterogeneity wa nyukiliotayidi zikuchokera DNA pa mlingo wa kulunjika sapereka zokhudza katundu kwachilengedwenso. Posachedwapa, chifukwa zosiyanasiyana nyukiliotayidi ndondomeko zenizeni mu magawo polynucleotide unyolo. Izi zikutanthauza kuti mudziwe majini ndiyotengera mu mamolekyulu DNA mu ndondomeko yeniyeni mayunitsi ake monomeric.

A DNA chikukhudza nyukiliotayidi mindandanda anafuna kuti mwambo ndi kuchotsa njira ya kaphatikizidwe wa DNA (kugawanika) ya RNA kaphatikizidwe (galamafoniyo) kaphatikizidwe mapuloteni (kumasulira). Pali mbali nyukiliotayidi kuti kutumikira wakumanga mphamvu yeniyeni ndi ochepetsera mamolekyulu zolimbana, komanso mbali nyukiliotayidi amene Musatenge mfundo iliyonse majini. Palinso kusinthidwa kuthengo, kuteteza mamolekyulu kuchokera nucleases.

Vuto la nyukiliotayidi mbali ya DNA sizinachitike kwathunthu kuthetsedwa. Khama la nyukiliotayidi mindandanda zidulo mkati ndi nthawi yambiri ndondomeko, amene amathandiza ntchito nuclease pogawanikana pamawere njira mamolekyulu enieni zidutswa osiyana. Pakali pano, lathunthu nyukiliotayidi ndondomeko ya zapansi ndi nitrogenous unakhazikitsidwa kuti ambiri tRNA chiyambi osiyana.

The DNA: kapangidwe yachiwiri

Watson ndipo Crick kuti cholinga chitsanzo cha helix awiri a deoxyribonucleic acid. Malinga ndi chitsanzo ichi, unyolo polynucleotide awiri entwine mzake, potero kupanga mtundu wa helix.

zapansi Nitrogenous iwo ili mkati kapangidwe, ndi phosphodiester msana - kunja.

The DNA: ukachenjede kapangidwe

The DNA liniya mu selo uli ndi mawonekedwe a molekyulu elongated, izo mmatumba mu dongosolo yaying'ono amatenga 1/5 zokha buku selo. Mwachitsanzo, DNA ya anthu asakhale ndi vutoli kutalika ndi 8 cm, nanyamula kuti kupsa mu khromozomu ndi kutalika 5 nm. stacking zinthu zimenezi chifukwa kukhalapo kwa nyumba helical DNA. Kuchokera pamenepa, ndizoonekeratu kuti onse awiri Shackleton DNA helix danga kungakhale zina stacking yeniyeni ukachenjede kapangidwe - superhelix. Supercoiled conformation ya DNA khalidwe la DNA ya zinthu apamwamba. Chotero dongosolo ukachenjede okhazikika ndi nsinga covalent kuti kwa amino zatsalira asidi amene amapanga mapulotini kupanga nucleoprotein zovuta (chromatin). Choncho, DNA ya maselo eukaryotic kugwirizana ndi mapuloteni makamaka zofunika khalidwe - histones, komanso mapulotini acidic ndi fosfoproteidami.