1iu ha s biu hin ca gen iu ha biu hin gen Prokaryote 1. iu ha mc phin m A. Lac operon B. Trp operon C. iu ha tng tng

2. iu ha mc dch m A. Khi u dch m B. Ko di dch m khc C. Tc phn r ca cc mRNA

Qu trnh kim sot gen Prokaryote i hi png nhanh vi nhng thay i ca mi trng. i vi eukaryote, s iu ha ca gen hngn vic duy tr cn bng ni mi mt mitrng bn trong n nh thch hp i mt vimi trng bn ngoi lc no cng thay i.C th a bo i hi nhng gen khc nhau vonhng thi im khc nhau ca qu trnh sinhtrng v pht trin trong s bit ha ca ccm Kim sot gen c th l dng c ngha lhot ha hot ng ca gen, hoc m kmhm s hot ng ca gen

iu ha s biu hin ca gen Prokaryote mc phin m

DNA mRNA Protein

M hnh Operon iu ha Phc hp gi l operon c m t vo nm 1961 bi Francois

Jacob v Jacques Monod. Mt operon c ba phn: promoter, operator v cc gen cu trc.

Thm vo l mt gen iu ha lin quan n vic cho php gencu trc c phin m hay khng

Operon Mt cm cc gene cu trc t di s kim sot ca mt vng iuha

Repressor binding site = operator RNAP binding site = promoter

promoter operator

Phc hp Operon

1.Promoter: c nhn din bi RNA polymerasel ni bt u qu trnh phin m

2.Operator: kim sot vic gn RNA polymerasevo promoterv thng thng nm trongpromoter hoc nm gia promoter v gen cnc phin m.

3.Gen cu trc: gene cu trc (hoc gen thit k)m ha cho chui polypeptide.

2Operon M hnh Operon iu ha Mt operon cm ng (inducible) cha mt cm gen cutrc thng thng dng ng (off), b kha birepressor ca n. Khi tc nhn kim sot gn vorepressor, tch n khi v tr kha gen(v th ngng cch). Gen sau tr thnh trng thi m (on) cho nkhi mt repressor gn tr li operator. Operon cmng- c hot ha bi cc phn t cm ng nh VD.Lac operon Mt operon c ch (repressible) cha mt cm gen cutrc thng thng dng m (on). Khi tc nhn kimsot gn vo repressor, repressor gn vo operator,kha gen cu trc v gen tr thnh trng thi ng(off).Operon c ch- b ng bi nhng cht ng km hm.VDTrp operon

Operon C ch iu ha gene Kim sot dng: qu trnh phin m ch xy rakhi promoter c hot ha bi activator

Kim sot m thng l c ch ph bin prokaryote

Kim sot dng thng ph bin eukaryote S t iu ha: protein iu ha qu trnh phinm ca chnh n

Kim sot dng:Kim sot dng = activator gn vo v tr iu ha kch thch qu trnh phin m gene, cn s c mt camt nhn t activator s phin m xy raKim sot m:Kim sot m = repressor gn ln b tr iu ha chnli qu trnh phin m ca geneS c mt ca nhn t repressor c ch qu trnh phinm, s phin m ch xy ra khi repressor b bt hot bimt inducerC hai kiu operon cm ng v c ch, gen ng khirepressor gn vo operator ca n. S khc bit lcch hot ng ca tc nhn kim sot repressor

Kim sot dng - Kim sot m

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3Kim sot dng: cm ngPhc hp activator- inducer gn lnv tr iu haXy ra s phinm

3/9/2009 13

Kim sot dng: c ch

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Phc hp activator- repressor khngth gn vi v triu haKhng phin m

Kim sot m: cm ngKhi inducer hindin, repressorkhng th gn lnv tr iu haXy ra s phinm

Allolactose, inducer3/9/2009 15

Kim sot m: c ch

Phc hp repressor-corepressor gn ln v triu haKhng phin m

Tryptophan, corepressor3/9/2009 16

Lactose operonOperon cm ng

Lac operon

4Lac Operon S biu hin ca gene l do cm ng haytheo chng trnh

Repressor thng c biu hin t geni

Repressor gn vo operator chn qutrnh phin m ca gene cu trc

Inducer lactose gn v lm bt hotrepressor cho php khi u qu trnhphin m

Lac Operon Lactose operator l mt v tr cn thit cho s cch

Lactose promoter l mt v tr cn thit cho sphin m

Lac operon cha vng gen cu trc lin kt vigene iu ha.

Lac Operon Cu trc cc protein ca lac operon:

Khi khng c lactose (controller), repressorgn vo operator c ch qu trnh phin mbng cch nng RNA polymerase gn vopromoter.

Khi c c cht, allolactose (controller), gn vo phn trepressor ang nm trn vng operator ca gene, khi repressor c tch khi gen. RNA polymerase c th gnvo promoter v gene m ha cho ba enzyme cn thitcho vic s dng lactose c phin m.

5Lac operon Khi cc enzyme c tng hp , lactose c s dng,bao gm c phn t allolactose gn vo repressor. Khiallolactose khng cn gn vo repressor protein,repressor kha promoter (bng cch gn vo operator),lm qu trnh phin m ngng. y l c ch kim sotm, bi v promoter b kha do operator b gn birepressor . Lactose operon l mt v d iu ha hot ng ca gencm ng, bi v khi hin din c cht ca con ngchuyn ha (metabolic pathway) c th cm ng qutrnh tng hp enzyme. Bi v allolactose cm ngphin m, lactose operon c gi l operon cm ng( hoc trong mt s trng hp, gi l operon c giic ch - derepressable operon v lactose lm ngnghot ng ca repressor).

Lac operon Hot ng ca gen c th c iu ha bi mt phn tactivator. Khng c phn t activator hin din, gen cphin m rt t.Lac operon cm ng hot ng trong h thng hot ngsong song vi mt activator, CRP (cyclic AMP receptorprotein), hay cn gi CAP (catabolite activator protein) kimsot lng glucose trong t boMc cAMP ni bo c mi tng quan t l nghch vi mcglucose. cAMP c th hot ha CRP. CRP l mt activatortrong Lac operon v trong mt s operon khc (nhng l mtrepressor cho chnh gene tng hp ra n).Dimer cAMP-CRP vi mt HTH motif gn vo DNA tiupstream ca Lac promoter v un cong vng DNA xungquanh n to iu kin thun li cho khi s phin m. (CRPmt mnh khng th gn vo DNA.)

Kim sot dng ca Lac operon

Lac Operon Lactose operon c mt phn ca kim sotdng

Kim sot dng ca lac operon lin quan ncAMP-CRP ( cyclic AMP receptor protein) gnvo promoter hot ha qu trnh phin mbi RNA polymerase

Phc cAMP-CRP iu ha hot tnh ca lacoperon

Khi mc glucose trong t bo xung thp, cAMP (cyclic adenosinemonophosphate), mt cht truyn tin th hai trong vic truyn tnhiu t bo tch ly li. cAMP gn vo v tr allosteric ca CRP hnhthnh mt phc CRP- cAMPCRP-cAMP gn vo v tr k lactose operon promoter v n lm RNApolymerase d dng gn vo vng promoter tng cng vic phinm cc enzyme lactase (nu lactose hin din s tch phn tlactose repressor).

6Tryptophan operonOperon c ch

Trp Operon

Trp operon cha cc gen cu trc cnthit cho qu trnh sinh tng hptryptophan

Trp operon hot ha qu trnh phin mkhi khng c s hin din ca tryptophan

H thng c ch c iu ha bi mtc ch kim sot ngc m

Trp Operon

7Trp Operon Trp operon c ng khi tryptophan gnvo v lm bt hot aporepressor

Phc hp tryptophan-repressor gn vooperator v ngn chn qu trnh phin mkhi mc tryptophan cao

Nu mc tryptophan st gim,phc hptrp-repressor s tch khi operator

Tryptophan, c gi l corepressor bi v n hot ng cng viprotein repressor kha s phin m, v operon tryptophan lmt operon c ch (repressible operon). y l mt c ch kimsot m bi v repressor nng chn qu trnh phin m

Gim bt (Attenuation)

Attenuation mt hnh thc rt nhy kthp vi s iu ha dch m ca trpoperon

Trnh t trp attenuator c cha mt trnht base b sung u 5 trong mRNA vc th bt cp b sung tao thnh cu trcthn (stem) v vng (loop)

Trp Operon - Gim bt(Attenuation)

Gim bt (Attenuation) S gim bt l nguyn nhn gy ra ktthc phin m sm mRNA v s hnhthnh cu trc kp tc ngng phin m vng u 5 ca mRNA

Nu tRNA-trp hin din , qu trnh tnghp peptide leader dn ti s bt cp bsung ca mRNA to thnh cu trc ngncn hot ng ca RNAP

8Gim bt (Attenuation) Ti nng thp ca tRNA-trp, ribosomeb tr hon, v mRNA c m v vy qutrnh phin m tip tc

iu ha gim bt cho php t bo png vi mc thay i ca mc tryptophan

9+ trpDNA

RNA Cu trc ngngphin m

RNA polymerase Ngngphin m

- trp

DNA

RNALeader peptide

DNA

RNA

Leader peptide

DNA

RNARNA polymerase

Phin mtip tc

Mt s Operon iu ha gim bt

iu ha tng tng(CASCADE REGULATION)

iu ha tng tng(CASCADE REGULATION)

Mt c ch iu ha nhanh chng v tit kim nnglng prokaryote l s dng cc nhc t khcnhau. Mi nh hng cho RNA polymerase xc nh vgn ln promoter. Nhng promoter ny kim sots biu hin ca nhng nhm genes lin quan nmt hot ng chuyn ha chuyn bit ca t bo. Sau y l hai v d v s iu ha biu hin cagen bng cch s dng cc nhn t sigma khcnhau

S dng lun phin nhn t bi E. coli cho s t iuchnh thch hp vi mi trng mi S dng lun phin nhn t bi SPO1 bacteriophagetrong sut qu trnh xm nhim

S dng lun phin nhn t E. coli trng thi bnh thng, RNA polymeraseholoenzyme cha 70, nhn t ph bin nht, snhn bit promoter ca cc gen cu trc hu ht lnh 70. Khi E. coli gp mi trng shock nhit (heat shock)do s tng ln t ngt nhit ca mi trng,mt nhn t mi, 32, c tng hp mt lngln v thay th cho 70 nh hng cho RNApolymerase gn vo heat- shock gene promoter. Snphm biu hin ca nhng gen ny gip cho t bochng li nhng nguy him do shock nhit. S gia tng hm lng 32 v :

(1) tng cng dch m mRNA 32 (2) S n nh ca protein 32.

Cc nhn t cng c lun phin s dng trongnhng hon cnh mi trng khc nhau biuhin cc gen khc nhau

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S dng lun phin nhn t bi SPO1bacteriophage trong qu trnh xm nhim

SPO1 phage xm nhim vo Bacillus subtilis c bc biu hin gene cc gen sm, trung gian v cc gene mun c biu hin nhngthi im khc nhau ca qu trnh xm nhim ca phage.

Cc gen sm ca phage c biu hin bi RNA polymerase ca vikhun vi vic s dng nhn t ca vi khun.

Mt trong nhng sn phm ca gene sm c biu hin l nhnt 28 ca phage. nhn t 28 ca phage s thay th nhn t ca vikhun nh hng RNA polymerase n cc promoter ca ccgene trung gian ca phage. Trong s sn phm ca cc gene trunggian c mt nhn t 34. Ti lt n, nhn t 34 tham gia vo qutrnh biu hin ca cc gene mun ca phage.

Kim sot phin m ca virus Virus s dng vt liu ca t bo ch nhn ln, phin m v dchm cc gene ca virus, ngay khi hot ha qu trnh ny chnh lnguyn nhn lm tan t bo ch. Phage n ha (temperate phage)c xc nh khi provirus tch khi DNA t bo ch v tr thnhdng lytic. Virus s lm ngng mi hot ng phin m v dch mb gen t bo ch. Kim sot di truyn ca Lamba () phage n ha c nghincu. Phage tr thnh dng lysogenic khi t bo ch trong mtmi trng thun li v chng c kh nng nhn ln nhanh chng.Khi t bo ch to nn nhiu th h mi, mi t bo mang mtphage . phage tr thnh dng tan khi t bo ch yu i. Hai virus protein, Cro v cI kim sot sc khe ca t bo ch.Khi t bo ch khe, cI protein tch ly hot ha chc nng genIysogenic gene v c ch chc nng gen Iytic. Khi t bo ch suyyu, Cro protein tch ly, s c ch chc nng gen Iysogenic vthc y hot ng ca gene Iytic. T l ca Cro vi cI quyt nhkhi no l phage s l Iysogenic hay Iytic. Cc virus khc c cch kim sot tng t.

Kim sot phin m ca virus Kim sot phin m ca virus

iu ha s biu hin ca gen Prokaryote mc dch m

DNA mRNA Protein

iu ha s biu hin ca gen Prokaryote mc dch m

prokaryotes, kim sot s biu hin cagen mc dch m da vo cc c chsau :

1. Hiu sut khi u dch m khc nhau donhng trnh t xung quanh start codon AUG

2. Hiu sut ko di dch m khc nhau dovic hnh thnh cu trc th cp trn mRNA

3. Tc phn r ca cc mRNA l khcnhau