Nhm 3 Lp 12DSH01

V Trng GiangV Th Thanh TrcNguyn ng Hoi VTrng Th Hng ThuPhan Th GnPhan Hng PhcNguyn Thy an ThanhNguyn Vn TnhPhm Minh KhoaTrn Th T Vy

CHNG 4TI BN DNA SI KP PROKARYOTE

**Ti bn DNA na gin onTi bn DNA mch kp kiu ti bn na gin on ( bn bo ton): Mt mch n ca phn t DNA c tng hp t mt mch bt ngun t DNA m v mch cn li c tng hp mi hon ton.

S ti bn DNA na gin on c tm hiu k nht l m hnh ca E.coli.

NHNG THNH PHN THAM GIA TI BN DNA Phn t DNA khunim khi uCc proteinCc nucleotideCc enzyme

ProteinDnaA: nhn bit v bm vo im khi u.DnaB v DnaC: c iu khin bi DnaA, bm vo im khi u v to phc hp khi u.Protein ti bn: h tr s ph v lin kt hydro.Pro SSB: gi cho 2 mch n khng lin kt vi nhau

Nucleotide4 loi nucleotide: dATP, dGTP, dCTP v dTTP l hp cht cao nng cung cp nng lng cho qu trnh ti bn.**Nucleotide c 3 vai tr:+ n v cu trc+ Trt t ca n l ni dung thng tin di truyn+ L ngun nng lng cho hat ng tng hp

Cc EnzymeDNA gyrase: m cun DNA siu xon pha trc mi chc ti bn. Primase v RNA polymerase : tng hp RNA mi.Cc DNA polymerase III xc tc chnh cho vic tng hp DNA mi nh c hot tnh xc tc: polymerase 3-5, mt s cn c hot tnh c sa. DNA polimerase I va ct b on mi i trc nh hot tnh ct b, va ko di on okazaki theo sau lp ch trng.. DNA ligase: hn gn khe h gia cc DNA mi bng cch hnh thnh cc lin kt 3 5 phosphodiester.

Giai on khi u Protein DnaA nhn ra im gc ( khi im ti bn) OriC, bm vo v bt u ph v cc lin kt hydro gia cc cp base ci xon.Nh lin kt ca DnaA OriC, cc DnaB v DnaC bm vo ti v tr OriC => to phc hp khi u ti bn.Enzyme gyrase tham gia h tr gin xon phn t DNA 2 pha ca DnaB.2 phn t helicase gn vo 2 si n v tip tc ph v cc lin kt hydro gia cc cp base ci xon DNA. Pro Rep bm vo si n dn u h tr vic ti bn si ny.Protein SSB gn ln cc mch n => 2 mch n khng th lin kt li vi nhau

S hnh thnh Primosome (mi)Mi l mt on RNA nh khong 10 nucleotide c tng hp bi phc hp protein enzyme.

S tng hp nh dng on bt u u 3 ca si chnh lm khun, v nhn ln cc im bt u trn si ph v to nn nhng on lai DNA RNA. Primosome sn xut cc RNA mi v to thnh u 5 ca mi on okazaki.

Tng hp si dn u

Khun l 3' - 5' ca DNA, sau khi to on RNA mi, cc nucleotide t do tip tc n gn vo u 3' - OH ca chui theo nguyn tc b sung vi chui lm khun nh DNA - polymerase III.DNA Polymerase III: xc tc s to thnh lin kt phosphodiester gia nhm 3-OH ca on mi v nguyn t P ca nucleotide triphosphate ang c gn vo on mi v tip tc polimer ha DNA.DNA Polymerase I: phn hy on mi v tng hp on mch thay th bng nguyn liu l cc nucleotide. Enzyme lygase to lin kt phosphor diester gia 2 nucleotide ca 2 mch.Tng hp cc si n DNA

Tng hp si theo sau

on RNA mi mi c tng hp nh primosome.DNA polymerase III tng hp ngc li 180o t vng lin kt RNA DNA.S tng hp tip tc cho n khi DNA pol III ni c t khong 1000 2000 deoxyribosenucelotide v tip gip vi on mi trc .DNA pol III ri khi khun ca si theu sau. Pro SSB cng c gii phng ngay sau .Khi DNA tip tc tng hp th DNA pol III tip tc gn vo v SSB cng gn vo theo.Sau , cc primosome khc s lin kt vi mch khun tng hp cc on mch mi v lp li chu k,.Khi c t 2 on Okazaki tr ln, DNA pol I s bt u hot ng: va polimer ha va c hot tnh exonuclease t u 5 n 3 bt u ni thm cc deoxyribosenucleotide v u 3 ca on, va loi b ribosenucleotide u 5 ca on Okazaki.Enzyme DNA lygase xc tc phn ng hnh thnh lin kt phosphodiester lin kt u 3 ca on Okazaki ny vi u 5 ca on Okazaki k tip.

Chc ti bn

Tng qut qu trnh Ti bn Prokaryote

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