Yuav ua li cas yog chromatin: txhais, qauv thiab muaj nuj nqi

Biochemical kev tshawb fawb nyob rau hauv noob caj noob ces - ib tug tseem ceeb txoj kev kawm nws cov ntsiab Cheebtsam - cov noob thiab chromosomes. Nyob rau hauv no tsab xov xwm peb yuav saib yog dab tsi chromatin, nrhiav tawm nws cov qauv thiab muaj nuj nqi nyob rau hauv lub cell.

Caj - lub ntsiab khoom teejtug uas yog nyob teeb meem

Ntawm cov ntsiab dab uas characterize lub kab uas nyob rau hauv lub ntiaj teb, yog ua tsis taus pa, kev noj haus, kev loj hlob, kev xaiv thiab tu tub tu kiv. Qhov kawg muaj nuj nqi yog ib lub tseem ceeb tshaj plaws rau lub preservation ntawm lub neej nyob rau lub ntiaj teb no. Yuav ua li cas tsis nco qab hais tias thawj lo lus txib uas muab los ntawm Vajtswv rau Adas thiab Eva cov nram qab no: "Nej yuav tsum fruitful thiab multiply." Nyob rau theem ntawm hlwb generative muaj nuj nqi yog tau nrog nucleic acids (constituent tshuaj ntawm chromosomes). Cov lug yuav tsum tau tham nyob rau hauv dab tsi li nram no.

Peb kuj ntxiv hais tias cov preservation thiab kis tau tus mob ntawm kev tshuaj ntsuam genetic ntaub ntawv nqa los ntawm lub xeeb leej xeeb ntxwv ntawm lub tib lub mechanism uas tsis nyob ntawm seb nyob rau theem ntawm lub koom haum ntawm cov neeg, uas yog rau cov kab mob thiab cov kab mob, thiab nws yog universal rau tib neeg.

Yuav ua li cas yog lub substance ntawm caj

Nyob rau hauv daim ntawv no peb kawm cov chromatin qauv thiab kev khiav dej num ntawm cov uas yog ncaj qha nyob rau hauv lub koom haum ntawm nucleic acid molecules. Swiss paub txog Miescher nyob rau hauv 1869 tebchaw tau kuaj nyob rau hauv lub nuclei ntawm hlwb ntawm lub cev, seeb thaj chaw ntawm acids hu ua lawv thawj nukleina thiab ces nucleic acids. Los ntawm lub standpoint ntawm Science News for KIDS, nws macromolecular compound - polymers. Cov monomers yog nucleotides muaj raws li nram no qauv: ib tug purine los yog pyrimidine puag, thiab pentose residue ntawm orthophosphoric acid. Zaum tau pom tias ob hom nucleic acids yuav tsum tam sim no nyob rau hauv lub hlwb: DNA thiab RNA. Lawv complexed nrog proteins uas kom tsim ib tug compound ntawm chromosomes. Raws li zoo raws li cov nqaijrog, nucleic acids muaj ntau theem ntawm spatial lub koom haum.

Nyob rau hauv 1953 lub Nobel nqi zog yog Watson thiab Crick deciphered lub qauv ntawm DNA. Nws yog ib tug qauv li ntawm ob chains sib thooj, los ntawm hydrogen bonds sawv ntawm nitrogenous bases rau lub hauv paus ntsiab lus ntawm complementarity (opposite adenine thymine puag nyob yam txawv cytosine - guanine). Chromatin qauv thiab muaj nuj nqi uas peb kawm, lub molecule comprises ib deoxyribonucleic acid thiab ribonucleic ntau yam configurations. Nyob rau qhov no qhov teeb meem, peb sib tham txog nyob rau hauv ntau yam lus hauv "Theem ntawm kev chromatin lub koom haum."

Localization ntawm lub substance ntawm caj nyob rau hauv ib lub cell

DNA tam sim no nyob rau hauv cov cytostructure li cov tub ntxhais, thiab kuj nyob rau hauv organelles, muaj peev xwm ntawm division - mitochondria thiab chloroplasts. Qhov no yog vim lub fact tias cov organelles ua qhov tseem ceeb functions nyob rau hauv lub cell: ATP synthesis, thiab cov synthesis ntawm piam thaj thiab oxygen tsim nyob rau hauv cog hlwb. Synthetic organelles kauj ruam niam txiv ob npaug lifecycle. Yog li, tus ntxhais hlwb nyob rau hauv mitosis (faib Somatic hlwb) los yog meiosis (lub tsim ntawm cov phev thiab ova) tsu cov yam arsenal cell lug muab lub hlwb nrog cov as-ham thiab lub zog.

Ribonucleic acid muaj ib saw thiab muaj ib tug tsawg dua molecular yuag tshaj DNA. Nws pom ob nyob rau hauv lub nucleus thiab nyob rau hauv hyaloplasm, thiab yog ib feem ntawm ntau cell organelles: ribosomes, mitochondria, endoplasmic reticulum, plastids. Chromatin nyob rau hauv cov organelles txuam nrog histone protein thiab ib feem ntawm cov plasmids - yeej kaw DNA molecules.

Chromatin qauv thiab

Yog li ntawd peb tau tsim muaj uas cov nucleic acid muaj nyob rau hauv lub tshuaj ntawm chromosomes - lub structural units ntawm caj. Lawv chromatin nyob rau hauv lub electron tshuab kuaj kab mob muaj hauv daim ntawv ntawm granular los yog filamentous lug. Nws muaj, dhau li ntawm tus DNA, thiab txawm RNA molecules, thiab proteins seeb yooj yim zog thiab muaj npe histones. Tag nrho cov saum toj no lug yog ib feem ntawm lub nucleosome. Lawv muaj nyob rau hauv lub nucleus thiab cov chromosomes yog hu ua fibrils (xov-solenoids). Ntsiab lus tag nrho cov saum toj no, peb txiav txim hais tias qhov no chromatin. Qhov no txoj compound ntawm deoxyribonucleic acids thiab tej cov nqaijrog - histones. Lawv, xws li lub coils, yog lub qhov txhab double-tso tseg DNA molecules tsim tau ib nucleosome.

Theem ntawm kev chromatin lub koom haum

caj tshuaj muaj ib tug txawv qauv, uas yog nyob ntawm ntau yam. Piv txwv li, nyob rau dab tsi theem ntawm lub neej voj voog niaj cell: faib lub sij hawm (metoz los yog meiosis), los yog hluavtaws presynthetic thaum lub sij hawm interphase. Los ntawm daim ntawv ntawm ib tug solenoid, los yog fibrils, raws li cov feem ntau yooj yim, muaj ib tug ntxiv compaction ntawm chromatin. Heterochromatin - ib tug ntau ntom lub xeev, yog tsim nyob rau hauv lub intron feem ntawm lub chromosome, uas yog tsis tau transcription. Thaum lub sij hawm so hlwb - interphase, thaum tsis muaj division txheej txheem - heterochromatin karyoplasm nyob rau hauv lub nucleus peripherally, nyob ze nws daim nyias nyias. Sealing nuclear txheem postsynthetic theem no tshwm sim nyob rau hauv lub neej voj voog ntawm lub hlwb, i.e. tam sim ntawd ua ntej division.

Yuav ua li cas txiav txim rau lub hws ntawm qhov teeb meem ntawm caj

Ntxiv rau lo lus nug "yog dab tsi chromatin," kev soj ntsuam pom tau tias nws yog nyob rau hauv lub foob-histone proteins uas, nrog rau cov lwg me me ntawm DNA thiab RNA nyob rau hauv lub nucleosome. Lawv muaj xws li plaub hom ntawm cov nqaijrog, hu ua nyuj thiab Linker. Thaum lub caij ntawm transcription (nyeem ntawv ntawm cov ntaub ntawv los ntawm noob ntawm RNA) caj khoom tsis zoo fused, thiab yog hu ua euchromatin.

Tam sim no kev faib ntawm DNA molecules txuam nrog histone proteins uas raug kawm. Piv txwv li, soj ntsuam ntawm pom tias chromatin txawv loci ntawm tib chromosome txawv muaj ntau seem ntawm cov hws. Piv txwv li, nyob rau hauv qhov chaw ntawm txuas mus rau lub mitotic ntxaiv chromosome filaments hu ua centromeres, nws yog ntau tuab tshaj cov telomeric seem - kawg loci.

Noob-regulators thiab chromatin

Lub tswvyim ntawm cov kev cai ntawm noob kev ua si, tsim los ntawm Fabkis geneticists Yakhauj thiab Monod, muab ib lub tswv yim ntawm lub hav zoov ntawm qhov chaw ntawm deoxyribonucleic acid, nyob rau hauv uas muaj yog tsis muaj cov lus qhia txog cov qauv ntawm cov protein. Lawv ua tau ib tug txhob txwm bureaucratic - managerial zog. Naming noob regulators, cov qhov chaw hauv lub chromosomes feem ntau nyob rau hauv nws cov qauv devoid-histone proteins. Chromatin, lub ntsiab txhais ntawm uas twb nqa tawm los ntawm sequencing, twb muaj npe qhib.

Nyob rau hauv ntxiv cov kev tshawb fawb nws pom hais tias nyob rau hauv cov loci nyob ib nucleotide ib theem zuj zus uas tiv thaiv kev ua raws li cov DNA molecules ntawm protein hais. Tej feem comprise cov ntxawg noob yog: promoters ehansery activators. Lub compaction ntawm chromatin mus rau hauv lawv siab, thiab qhov ntev ntawm cov khej feem 300 nm. Muaj yog ib txoj kev rau kev txiav txim lub biochemical qhib chromatin nyob rau hauv cais nuclei nyob rau hauv uas ntawm kev siv ntawm DNA-ASE enzyme. Nws sai sai lov loci ntawm chromosomes, tsis-histone proteins. Chromatin nyob rau hauv cov chaw no tau raug hu ua hypersensitive.

Lub luag hauj lwm ntawm caj tshuaj

Ceg nrog DNA, RNA thiab protein hu ua chromatin, muab kev koom tes nyob rau hauv cell ontogeny thiab hloov nws muaj pes tsawg leeg nyob rau hauv lub cev nqaij thiab nyob rau theem ntawm kev loj hlob ntawm ib tug kab mob raws li ib tug tag nrho. E.g., nyob rau hauv lub epithelial hlwb ntawm daim tawv nqaij xws noob li ehanser thiab pab txhawb sim cov nqaijrog repressors, thiab cov tswj txoj cai noob nyob rau hauv lub secretory hlwb ntawm lub plab hnyuv epithelium thiab yog active nyob rau hauv lub cheeb tsam ntawm qhib chromatin. Zaum, geneticists pom tias nyob rau ib feem ntawm DNA uas tsis encode cov nqaijrog, ris rau ntau tshaj 95% ntawm cov tib neeg genome. Qhov no txhais tau tias lub noob tswj yog ntau npaum li cas dua li cov uas yog lub luag hauj lwm rau lub synthesis ntawm peptides. Cov kev taw qhia ntawm hom kev kawm xws li DNA daim tawv nyias thiab sequencing tso cai mus nrhiav tau tawm yog dab tsi cov chromatin, thiab raws li ib tug tshwm sim, rau daim duab qhia cov tib neeg genome.

Kev tshawb fawb ntawm chromatin yog ib qho tseem ceeb nyob rau hauv xws chaw ntawm science xws li tib neeg noob caj noob ces thiab kev kho mob noob caj noob ces. Qhov no yog txuam nrog ib tug sharply nce qib ntawm tshwm sim ntawm roj ntsha kab mob - xws li noob thiab chromosome. Early nrhiav kom tau ntawm cov syndromes tsub kom qhov feem pua ntawm zoo forecasts nyob rau hauv lawv cov kev kho mob.