Yuav ua li cas yog lub reduplication ntawm DNA? Tus txheej txheem ntawm DNA replication

Cov DNA molecule - yog nyob rau hauv chromosome qauv. Ib tug chromosome muaj ib zaug xwb molecule muaj ob strands. Reduplication ntawm DNA - yog cov kev hloov ntawm cov lus qhia tom qab nws tus kheej-tu tub tu kiv ntawm threads los ntawm ib tug qauv rau lwm tus. Nws yog xam qhovkev nyob rau hauv ob qho tib si DNA thiab RNA. Qhov tsab xov xwm no tham txog lub DNA replication txheej txheem.

General ntaub ntawv thiab hom ntawm DNA synthesis

Nws yog lub npe hu hais tias cov xov nyob rau hauv lub molecule. Txawm li cas los, thaum tus txheej txheem ntawm DNA replication pib, lawv dispiralized, ces cov kauj ruam cia tseg, thiab nyob rau txhua daim ntawv tshiab yog tsim. Tomqab kawm tas muaj ob tag zoo tib yam molecules, txhua tus uas muaj ib tug niam txiv thiab ib tug me nyuam thread. Qhov no synthesis yog hu ua semi-conservative. DNA molecules yeej, thaum uas seem nyob rau hauv ib centromere, thiab thaum kawg diverge tsuas yog thaum no centromere division txheej txheem yuav pib.

Tus lwm yam yog hu ua reparative synthesis. Nws, tsis zoo li yav dhau los ib tug, yog tsis txuam nrog tej cell theem, tab sis pib nyob rau hauv cov kev tshwm sim ntawm DNA puas tsuaj. Yog hais tias lawv yog ib yam nkaus thiab dav-xws li xwm, lub cell nws thiaj li tuag. Txawm li cas los, Yog hais tias qhov kev puas tsuaj yog lub zos, ces koj yuav tsa tau lawv rov. Nyob ntawm seb qhov teeb meem yuav tsum tau rov qab los los yog cais ob tug strands ntawm DNA nyob rau ib zaug. Qhov no, raws li nws yog hu ua, unscheduled synthesis tsis coj ib tug ntev lub sij hawm thiab yuav tsis tau ib tug ntau ntawm lub zog.
Tab sis thaum muaj ib tug reduplication ntawm cov DNA, ces siv ib tug ntau ntawm lub zog, khoom, ncav us txog qhov ntev ntawm nws saib.
Reduplication yog muab faib ua peb lub sij hawm:

• pib;
• elongation;
• txiav.

Cia peb xav txog ib theem zuj zus ntawm DNA replication.

pib

Nyob rau hauv tib neeg DNA - ib tug ob peb kaum ntawm lab ntawm cov puag officers (cov tsiaj lawv suav xwb ib puas thiab cuaj). DNA reduplication pib nyob rau hauv ntau qhov chaw hauv cov saw hlau rau cov nram qab no yog vim li cas. Nyob ib ncig ntawm tib lub sij hawm nyob rau hauv lub RNA transcription tshwm sim, tab sis nyob rau hauv lub synthesis ntawm DNA yog tshem tawm nyob rau hauv ib co ntawm cov xaiv qhov chaw. Yog li ntawd, xws li ib tug txheej txheem ua ntej ib tug txaus tus nqi ntawm cov tshuaj yeeb dej caw accumulates nyob rau hauv lub cytoplasm ntawm hlwb nyob rau hauv kev txiav txim kom them nyiaj yug noob qhia thiab cellular kev ua si uas tsis tau tawg. Nyob rau hauv view ntawm no, cov txheej txheem yuav tsum muab qhov chaw raws li sai li sai tau. Tshaj tawm hauv xov thaum lub sij hawm lub sij hawm no nqa tawm, thiab lub transcription yog tsis ua. Kev tshawb fawb tau qhia tias DNA reduplication tshwm sim ib zaug nyob rau hauv ob peb txhiab ntsiab lus - chaw me me muaj ib lub nucleotide ib theem zuj zus. Lawv tuaj koom los ntawm tshwj xeeb initiator cov nqaijrog, uas nyob rau hauv lem yog koom los ntawm lwm yam enzymes ntawm DNA replication.

Cov DNA fragment uas yog tsim yog hu ua ib tug replicon. Nws pib los ntawm qhov pib thiab xaus rau thaum lub enzyme terminates replication. Replicon yog siv yooj yim, thiab kuj cov khoom siv rau tag nrho cov txheej txheem ntawm nws tus kheej software.
Cov txheej txheem yuav tsis pib los ntawm tag nrho cov ntsiab lus ntawm ib zaug, qhov chaw nws pib ua ntej lawm, qhov chaw - yav tom ntej; Nws tau coj qhov chaw nyob rau hauv ib los yog nyob rau hauv ob opposite qhia. Cov txheej xwm coj qhov chaw nyob rau hauv lub nram qab no thaum cov duab:

• replication tib rab diav rawg;
• RNA primer.

replication diav rawg

Qhov no yog ib feem pib ib tug txheej txheem nyob rau hauv lub kaw yarns yog tsim DNA deoxyribonucleic filaments. Plugs li rau thiaj li hu ua lub qhov muag ntawm replication. Cov txheej txheem yog preceded los ntawm ib tug xov tooj ntawm cov ua:

• tso los ntawm kev twb kev txuas nrog histones nyob rau hauv ib tug nucleosome - enzymes xws li ib tug DNA replication methylation, acetylation, thiab ntsev tsim tshuaj uas ua rau cov nqaijrog poob nws zoo xwb uas tswj lawv tso tawm;
• despiralization - yog unwinding, uas yog tsim nyog rau qhov ntxiv liberation ntawm threads;
• tawg hydrogen bonds ntawm DNA strands;
• lawv divergence nyob rau hauv qhov sib txawv sab ntawm lub molecule;
• fixation tshwm sim siv SSB proteins.

RNA primer

Synthesis yog ib qho enzyme hu ua DNA polymerase. Txawm li cas los, yuav pib nws tus kheej nws tsis tau, thiaj li ua lwm yam enzymes - lub RNA polymerase, uas tseem hu ua RNA primers. Lawv tsim nyob rau hauv thaum uas tig mus strands ntawm deoxyribonucleic rau lub hauv paus ntsiab lus ntawm complementarity. Yog li, qhov pib ntawm RNA synthesis ntawm ob xaus, ob primers thiab tau ncaim mus lawm torn sib nrug heev DNA strands.

elongation

Qhov no lub sij hawm yog pib los ntawm nucleotide ntxiv thiab 3 'kawg ntawm lub RNA-primer, uas yog tus twb hais DNA polymerase. Nws hniav ua ntej thib ob, thib peb nucleotide, thiab hais txog. Tshiab strands yog kev cob cog rua rau lub hauv paus ntawm tus niam txiv saw los ntawm hydrogen bonds. Nws yog ntseeg hais tias lub synthesis ntawm cov xov yog nyob rau hauv lub 5 '- 3'.
Qhov uas nws tshwm sim nyob rau hauv cov kev taw qhia ntawm replication tib rab diav rawg, synthesis hais tsis tu ncua thiab yog li lengthens. Yog li ntawd, cov xov no yog hu ua tus ua los yog ua. Nws RNA primer yog tsis tsim.

Txawm li cas los, nyob rau sab strand ntawm niam txiv DNA nucleotides tseem mus koom nrog cov RNA primer, thiab deoxyribonucleic saw yog tsim nyob rau hauv kev coj rov qab los ntawm cov replication diav rawg. Nyob rau hauv cov ntaub ntawv no, nws yog hu ua ncua los yog lagging.

Nyob rau lagging strand synthesis tshwm sim nyob rau hauv cov tawg tsam, nyob rau ib kawg ntawm lub synthesis pib nyob rau lwm qhov chaw nyob ze rau siv tib RNA primer. Yog li, muaj ob ncua saw fragment yog koom DNA thiab RNA. Lawv hu ua Okazaki tawg tsam.

Ces txhua yam yog rov qab. Ces spliced lwm lem ntawm lub helix, hydrogen tawg kev sib txuas lus xov mus rau tej sab, ua saw lengthened nyob rau lagging tsim nram qab no fragment RNA primer, whereupon - Okazaki fragment. Tom qab ntawd, nyob rau hauv lub ruamqauj RNA primer strands yuav raug rhuav tshem thiab cov DNA tawg tsam yog koom rau ib tug. Yog li no Circuit Court yuav siv sij hawm qhov chaw nyob rau tib lub sij hawm:

• lub tsim los ntawm cov tshiab RNA primer;
• synthesis ntawm Okazaki tawg tsam;
• kev puas tsuaj ntawm RNA primers;
• rov qab sib koom rau hauv ib Circuit Court.

txiav

Tus txheej txheem ntxiv raws li ntev li ob tsis tau raws li lub replication diav rawg, los yog ib tug ntawm lawv yuav tuaj mus rau qhov kawg ntawm lub molecule. Tom qab lub rooj sib tham, tib rab diav rawg DNA ntxhais kawm yog koom los ntawm cov enzyme. Nyob rau hauv cov ntaub ntawv, yog hais tias tus plug yog mus ntawm lub kawg ntawm lub molecule, DNA reduplication lawm siv tshwj xeeb enzymes.

kho

Nyob rau hauv tus txheej txheem no, ib qho tseem ceeb luag hauj lwm yog muab rau cov kev tswj (los yog kho) ntawm replication. Muab synthesis tau txais tag nrho plaub hom nucleotides, thiab cov kev sojntsuam los ntawm cov DNA polymerase pairing xaiv cov neeg uas yuav tsum tau.

Cov kev kawm nucleotide yuav tsum tau tsim hydrogen bonds raws li zoo xws li cov nucleotide rau lub template DNA strand. Tsis tas li ntawd, ntawm lub qab zib-phosphate qaum yuav tsum muaj ib yam tsis tu ncua deb coj mus rau peb rings nyob rau hauv ob bases. Yog hais tias lub nucleotide tsis tau raws li cov uas yuav tsum tau, lub kev twb kev txuas yuav tsis tshwm sim.
Control yog nqa tawm ua ntej nws yog incorporated rau hauv lub Circuit Court thiab ua ntej txoj siav nyob rau hauv cov tom ntej nucleotide. Tom qab hais tias, cov kev twb kev txuas mus rau lub caj qaum saharofosfata.

mutational variability

Lub mechanism ntawm DNA replication, dua li cov feem pua ntawm cov neeg yog ib txwm teeb nyob rau hauv lub filaments, uas yog hu ua feem ntau "noob change." Hais txog ib txhiab puag officers, muaj yog ib tug yuam kev hais tias konvariantnaya hu ua reduplication.

Nws tshwm sim rau txawv yog vim li cas. Piv txwv li, nyob rau high school los yog ib yam nkaus thiab uas tsis muaj ntau ntawm nucleotides deamination ntawm cytosine, muaj cov mutagens nyob rau hauv lub synthesis ntawm ob leeg. Nyob rau hauv tej rooj plaub, qhov yuam kev yuav kho los ntawm kev kho dab nyob rau hauv lwm yam kev kho yuav tsis yooj yim sua.

Yog hais tias qhov kev puas tsuaj cuam tshuam rau cov pw tsaug zog qhov chaw, ib qho yuam kev yuav tsis muaj teeb meem loj yuav tshwm thaum muaj DNA replication txheej txheem. Nucleotide ib theem zuj zus ntawm ib lub noob yuav tshwm sim nrog pos yuam kev. Ces nws tsis yog cov ntaub ntawv, thiab ib tug tsis zoo tshwm sim muaj peev xwm ua tau zoo li txoj kev tuag ntawm lub cell, thiab txoj kev tuag ntawm tag nrho cov kab mob. Nws yuav tsum raug borne nyob rau hauv lub siab hais tias noob change yog raws li nyob rau hauv mutational variability, uas ua rau cov noob pas dej ua ke ntawm plasticity.

methylation

Thaum lub sij hawm ntawm synthesis, los yog tam sim ntawd tom qab nws tshwm sim methylation chains. Nws yog ntseeg hais tias tus txheej txheem no yog tsim nyog rau ib tug neeg mus rau daim ntawv chromosomes thiab tswj noob transcription. Nyob rau hauv tus txheej txheem no cov kab mob ntawm DNA ua hauj lwm pab txoj kev tiv thaiv tiv thaiv txiav enzymes.