Cov DNA molecule: lub theem ntawm cov yam ntxwv lub koom haum

DNA Molecule - ib tug polynucleotide monomer units uas yog plaub deoxyribonucleotide (dAMF, dGMP, dCMP thiab dTMP). Qhov ratio ntawm ib theem zuj zus ntawm cov nucleotides rau hauv lub DNA sib txawv ntawm cov kab mob yog cov. Dhau li lub ntsiab nitrogenous bases nyob rau hauv DNA kuj muaj lwm yam me bases deoxyribonucleotides nrog 5-methylcytosine, 5-oksimetiltsitozin, 6-methylaminopurine.

Thaum muaj ib tug ploj ntawm kev siv cov qauv ntawm cov X-ray crystallography kawm lom macromolecules thiab tau zoo meej X-ray, nws twb tau mus nrhiav kom paub cov molecular qauv ntawm DNA. Hais tias txoj kev yog raws li nyob rau hauv lub fact tias ib tug beam ntawm thaum uas tig mus X-rays teeb meem rau ib tug crystalline pawg atoms, cov ntaub ntawv ib tug diffraction txawv, uas mas nyob ntawm lub atomic luj ntawm lub atoms, thiab lawv qhov chaw nyob rau hauv qhov chaw. Nyob rau hauv lub 40s ntawm lub xeem caug xyoo, lub hom phiaj ntawm peb-dimensional qauv ntawm cov DNA molecule tau raug muab tso rau pem hauv ntej. U. Astbury muaj pov thawj hais tias tus deoxyribonucleic acid yog ib pawg ntawm cov superimposed tiaj nucleotides.

Lub hom qauv ntawm cov DNA molecule

Nyob rau hauv cov thawj cov qauv ntawm nucleic acids, yog meant ib theem zuj zus ntawm nucleotides nyob rau hauv lub polynucleotide kho DNA saw. Nucleotides yog txuas ua ke los ntawm phosphodiester bonds uas yog tsim nyob rau nruab nrab ntawm cov OH pab pawg neeg nyob rau 5 txoj hauj lwm ntawm ib tug nucleotide thiab deoxyribose lub OH-pab pawg neeg nyob rau hauv txoj hauj lwm 3 ntawm lwm pentose.

Lub lom thaj chaw ntawm lub nucleic acid piv txiav txim los ntawm lub zoo thiab raws li tus nucleotide ib theem zuj zus ntawm lub polynucleotide saw.

Lub nucleotide muaj pes tsawg leeg ntawm DNA los ntawm cov kab mob ntawm txawv taxonomic pawg no yog hais thiab yog txiav txim los ntawm lub ratio (G + C) / (A + T). Siv tau tseem tau txiav txim los ntawm cov neeg kawm ntawv ntawm heterogeneity ntawm lub nucleotide muaj pes tsawg leeg ntawm DNA los ntawm cov kab mob ntawm txawv keeb kwm. Yog li, nyob rau hauv ntau dua cov nroj tsuag thiab cov tsiaj ratio (G + C) / (A + T) mas nws txawv me ntsis thiab muaj ib tug nqi siab tshaj 1. kab mob tseem coefficient txawv lug - los ntawm 0.35 mus 2,70. Txawm li cas los, Somatic hlwb ntawm ib tug tsiaj ntawm DNA muaj qhov tib nucleotide muaj pes tsawg leeg, piv txwv li. E. Peb yuav hais tias cov ntsiab lus ntawm GC officers ntawm bases ntawm DNA ntawm ib hom yog zoo tib yam.

Kev txiav txim ntawm heterogeneity ntawm lub nucleotide muaj pes tsawg leeg ntawm DNA ntawm ib tus nqi ntawm tseem tsis muab ntaub ntawv hais txog nws lom zog. Tsis ntev los no, vim qhov sib txawv kev nucleotide ib theem zuj zus nyob rau hauv ib tug polynucleotide saw feem. Qhov no txhais tau hais tias kev tshuaj ntsuam genetic ntaub ntawv kho nyob rau hauv DNA molecules nyob rau hauv ib lub ib theem zuj zus ntawm nws monomeric units.

Ib tug DNA molecule muaj nucleotide sequences npaj rau qhov pib thiab txiav dab ntawm synthesis ntawm DNA (replication) ntawm RNA synthesis (transcription) protein synthesis (translation). Muaj nucleotide sequences uas yuav pab tau rau khi tej activating thiab inhibitory ntxawg molecules, raws li zoo raws li nucleotide sequences uas tsis nqa tej kev tshuaj ntsuam genetic ntaub ntawv. Muaj kuj hloov lub teb, uas tiv thaiv lub lwg me me los ntawm nucleases.

Qhov teeb meem ntawm lub nucleotide sequences ntawm DNA tsis tau tau kiag li solved. Kev txiav txim ntawm nucleotide sequences ntawm nucleic acids yog lub sij hawm-siv txoj kev, uas yuav muab cov kev siv ntawm nuclease cleavage txoj kev molecules rau cais tawg tsam. Rau hnub tim, lub teb nucleotide ib theem zuj zus ntawm lub nitrogenous bases tsim rau feem ntau ntawm tRNA txawv keeb kwm.

Cov DNA molecule: theem nrab qauv

Watson thiab Crick tau tsim ib tug qauv ntawm lub ob helix ntawm deoxyribonucleic acid. Raws li cov qauv no, qhov ob polynucleotide chains entwine txhua lwm yam, li no txoj kev ua ib tug zoo ntawm helix.

Nitrogenous bases lawv nyob hauv tus qauv, thiab ib tug phosphodiester qaum - nraum zoov.

Cov DNA molecule: tertiary qauv

Lub linear DNA nyob rau hauv lub cell muaj tus duab ntawm ib tug elongated molecule, nws yog fej nyob rau hauv ib tug compact qauv thiab yuav siv sij hawm li tsuas yog 1/5 ntawm cov cell volume. Piv txwv li, lub DNA ntawm tib neeg chromosome ntev yog 8 cm, thiab tau ntim rau li uas haum mus rau hauv ib tug chromosome nrog ib tug ntev ntawm 5 nm. Tej tso yog tau vim lub xub ntiag ntawm lub helical DNA lug. Los ntawm no nws hais ntxiv hais tias lub ob-tso tseg DNA helix nyob rau hauv qhov chaw yuav ua tau ntxiv stacking ib lub tertiary qauv - superhelix. Supercoiled conformation ntawm cov DNA cov yam ntxwv ntawm cov chromosomes siab tus kab mob. Tej tertiary qauv stabilized los ntawm covalent bonds rau cov amino acid residues hais tias ua li cov proteins uas rau nucleoprotein complex (chromatin). Yog li ntawd, cov DNA ntawm eukaryotic hlwb txuam nrog cov nqaijrog mas yooj yim cim - histones, raws li zoo raws li acidic cov nqaijrog thiab fosfoproteidami.