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Expresia genelor

ADN ARNm Protein

ARNr

ARNt

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TP +1 18S 5,8S 28S

Transcripie

Processing (autosplicing)

18S 5,8S 28S

ADN

proARNr

ARNr

Etapele expresiei genelor de clasa I

Asamblarea 40S i 60S

18S + 33 proteine = 40S 28S + 5,8S + 5S+ 49 proteine = 60S

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TP

Transcripie

Transferul RNP n citoplasm

Etapele expresiei genelor de clasa IIE E E EI I IADN

proARNm

Processing-ul ARNm

ARNm 7MeGppp AAAAAAAAAAAAA..........

Translaie

Conformaia proteinei

7MeGppp AAAAAAAAAAAAA..........

Protein

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Transcripie

Transferul ARNtn citoplasm

Etapele expresiei genelor de clasa III (ARNt)

Processing-ul ARNt

A

TADN

B

+1

proARNt

ARNt

Formarea aminoacil-ARNtAminoacil-ARNt

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Transcripia.

Processing-ul ARN

la eucariote

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Transcripia reprezint procesul molecular

de copiere a informaiei genetice

nregistrate n ADN prin sintezamoleculelor de ARN

5-ATTGCATGATTACCATGTA-3 Catena codogen (netranscris)

3-TAACGTACTAATGGTACAT-5 Catena anticodogen (transcris)

5-AUUGCAUGAUUACCAUGUA-3 ARN

Transcripie (ARN-polimeraza)

*** Principiile transcripiei:! Sintez matricial! Complementar! Antiparalel! Unidirecionat

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APARATUL DE TRANSCRIPIE

I. Secvene ADNa) codificatoare; a) transcrise a)translate

b) reglatoare b) netranscrise b) netranslatec)modulatoare;

II. EnzimeARN-polimeraza I Mg++, Ca++

ARN-polimeraza II

ARN-polimeraza III Mn++

III. Uniti de polimerizareATP, GTP, CTP, UTP

IV. Factori de transcripie:

a)GENERALIpentru o anumit clas de genegene cl. I gene cl. II gene cl. IIIUBF TF II D (TBP) TF III ASL 1 TF II A TF III C

TF II B TF IIIB

TF II F; E; Hb) SPECIFICIgenei transcrise

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Etape Factori responsabili Produs LoculdesfurriiTranscripia ARN-polimeraza II +

TF II D,A,B ..Pre-ARNm Nucleu

Procesing-ula) CAP-area

b) Poliadenilareac) Splicing-ul

Guanilat-transferazaEndonuceaza

PoliA-sintetazaSpliceosoma U1-6

ARNm Nucleu

Transferul ARNm Proteine de transferMediatoriligand(poliA) + receptor (pr.por)

RNP(informosoma)

N C

Translaia ARNm - cod geneticARNtRibosomi

Polipeprid Citoplasm

Maturizareaproteinei

TransferazeChaperoni

Proteinbiologic activ

Citoplasm

Etapele expresiei genelor structurale(de clasa II) la eucariote

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TRANSCRIPIA GENELOR STRUCTURALE LA EUCARIOTE

1. Iniierea- formarea complexului de iniiere a transcripiei- identificarea +1 i a direciei de transcripie- formarea complexului deschis- identificarea matriei (catena anticodogen)

2. Elongarea- alunecarea ARN-polimerazei pe matria ADN n direcia 3-5- sinteza ARN n direcia 5- 3

3. Terminarea- copierea secvenei terminatorului- ncetinirea ARN-polimerazei- RF disociaz complexul ARN-polimeraz ADN - ARN

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-10-20-30-40 +1 +10 +20 +30

TAFs

TFIID

TFIIA

TFIIB

ARN-Polimeraza II

TFIIF

TFIIE

Iniierea transcripiei genelor de clasa II

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Terminarea transcripiei

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T

CAP-are

Processing-ul ARNm la eucarioteE E E EI I I

proARNm

Poliadenilare

7MeGppp

7MeGppp AAAAAA..

ARNm

7MeGppp AAAAAA..

Splicing

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CAP-area ARNm

* Adugarea unei GTPmetilat (7MeGTP)

* realizat de enzima

guanilattransferaza

* prin legtur 5ppp5

CAP-ul:

! Stabilizeaz captul 5al

ARNm

! Reprezint situs de

recunoatere a ARNm

pentru ribosomi

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Poliadenilare

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Splicing

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Tipurile splicingului ARNm

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Electronograma procesului de transcripie a

genelor de clasa I n nucleol

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Iniierea transcripiei la procariote

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