El Dogma Central

El Dogma Central de la Biología Molecular describe un proceso de

dos pasos, la transcripción y la traducción, por el cual la información

contenida en los genes se transforma en proteínas.

ADN ARN proteínas

TRANSCRIPCION

TRADUCCION

DNA

mRNA

Ribosoma

Polipeptido

DNA

Pre-mRNA

celula procariotica

Envoltura

Nuclear

mRNA

TRADUCCION

TRANSCRIPTION

PROCESAMIENTO RNA

Ribosoma

Polipeptido

Eukaryotic cell

TRANSCRIPCIONDNA

TRADUCCION

Ribosoma

Polipeptido

mRNA

Celula Procariotica

LE 17-3-5

TRANSCRIPTION

TRANSLATION

DNA

mRNA

Ribosome

Polypeptide

DNA

Pre-mRNA

Prokaryotic cell

Nuclear

envelope

mRNA

TRANSLATION

TRANSCRIPTION

RNA PROCESSING

Ribosome

Polypeptide

Eukaryotic cell

DNA

molecula

Gen 1

Gen 2

Gen 3

DNA cadena

(templada)

3

TRANSCRIPCION

Codon

mRNA

TRADUCCION

Proteina

Amino acido

35

5

Elongacion No-templada

Cadena devDNA

RNA

polimerasa

RNA nucleotidos

3 end

3

5

5

Nuevo RNA

Cadena templado

ADN

Direccion de transcripcion

(“downstream”)

Promotor

53

RNA polimerasa

Punto de iniciacion

DNA

Unidad Transcripcion

35

53

35

Unwound

DNA

RNA

tran-

script

Template strand

of DNA

Iniciacion

Elongacion

Terminacion

53

35

53

35

35

Rewound

DNA

RNA

transcripto

5

Completo RNA transcript

LE 17-8

Promoter

53

35

TATA box Start point

Transcription

factors

53

35

Several transcription

factors

Additional transcription

factors

RNA polymerase IITranscription factors

RNA transcript

53

355

Transcription initiation complex

Eukaryotic promoters

Template

DNA strand

LE 17-11

Exon 15

Intron Exon 2

Other proteins

Protein

snRNA

snRNPs

RNA transcript (pre-mRNA)

Spliceosome

5

Spliceosome

componentsCut-out

intron

mRNA

Exon 1 Exon 25

Exon 15

Intron

Otras proteinas

Proteina

snRNA

snRNPs

RNA transcripto (pre-mRNA)

Spliceosoma

Exon 2

5

Spliceosoma

Corte-out

intron

mRNA

Exon 1 Exon 25

componentes

Spliceosoma

Gen

Transcripcion

Procesamiento RNA

Traduccion

Dominio 2

Dominio 3

Dominio 1

Polipeptido

Exon 1 Intron Exon 2 Intron Exon 3

DNA

LE 17-9

5

Protein-coding segment

5 Start codon Stop codon Poly-A tail

Polyadenylation signal

5 3Cap UTR UTR

LE 17-10

5 Exon Intron Exon Intron Exon 3

Pre-mRNA

1 30 31 104 105 146

Coding

segment

Introns cut out and

exons spliced together

1 146

5 Cap

5 Cap

Poly-A tail

Poly-A tail

5 3UTR UTR

Codón iniciación Codón StopCodón

Cola

(no traducido)Fragmento lectura

(traducido)

Guía

(no traducido)

LE 17-13

Polypeptide

tRNA with

amino acid

attached

Ribosome

tRNA

Anticodon

35

mRNA

Amino

acids

Codons

Sitio de union

Amino acido

Puentes

Hydrogeno

3

5

estructura dos dimensionesAnticodon

Sitio de union

Amino acido

3

5

Puentes

Hidrogeno

Anticodon Anticodon

Simbolo usadoEstructura tres dimensiones

3 5

Amino acidoAminoacil-tRNA

sintetasa (enzima)

Pirofosfato

Fosfatos

tRNA

AMP

Aminoacil tRNA

(un “activado

amino acido”)

sitio P (Sitio ligadura

Peptidil-tRNA)

sitio E

(sitio salida)

Sitio ligadura

mRNA

Sitio A (sitio de ligadura

Aminoacyl-tRNA)

Subunidad

mayor

Subunidad

menor

Schematic model showing binding sites

E P A

LE 17-5

Second mRNA base

Th

ird

mR

NA

bas

e (

3e

nd

)

LE 17-16

Amino end

mRNA

5

3

Growing polypeptide

Next amino acidto be added topolypeptide chain

tRNA

Schematic model with mRNA and tRNA

Computer model of functioning ribosome

53

E

Codons

Schematic model showing binding sites

Small

subunit

Large

subunit

A site (Aminoacyl-

tRNA binding site)E site

(Exit site)

E P A

mRNA

binding site

P site (Peptidyl-tRNA

binding site)

Small

subunit

Large

subunit

Exit tunnelGrowing

polypeptidetRNA

molecules

E P A

mRNA

LE 17-16a

tRNA

molecules

Exit tunnelGrowing

polypeptide

Large

subunit

mRNA 3

Computer model of functioning ribosome

Small

subunit

5

E P A

INICIACION

GTPInitiator tRNA

mRNA

53

mRNA binding site

Small

ribosomal

subunit

Start codon

P site

53

Translation initiation complex

E A

Large

ribosomal

subunit

GDP

LE 17-16c

Amino end

mRNA

5

3

Growing polypeptide

Next amino acid

to be added to

polypeptide chain

tRNA

Codons

Schematic model with mRNA and tRNA

E

ELONGACION

Ribosome ready for

next aminoacyl tRNA

mRNA

5

Amino end

of polypeptide

E

Psite

Asite

3

2

2 GDP

E

P A

GTP

GTP

GDP

E

P A

E

P A

TERMINACION

Release

factor

Stop codon

(UAG, UAA, or UGA)

5

3

5

3

5

Free

polypeptide

3

When a ribosome reaches a stop

codon on mRNA, the A site of the

ribosome accepts a protein called

a release factor instead of tRNA.

The release factor hydrolyzes the

bond between the tRNA in the

P site and the last amino acid of the

polypeptide chain. The polypeptide

is thus freed from the ribosome.

The two ribosomal subunits

and the other components

of the assembly dissociate.

LE 17-20

Ribosomes

mRNA

This micrograph shows a large polyribosome in a prokaryotic cell (TEM).

An mRNA molecule is generally translated simultaneously

by several ribosomes in clusters called polyribosomes.

Incoming

ribosomal

subunits

Growing

polypeptides

End ofmRNA(3 end)

Start ofmRNA(5 end)

Completed

polypeptides

m0.1 m

LE 17-20a

Incoming

ribosomal

subunits

Growing

polypeptides

Completed

polypeptide

Start of

mRNA

(5 end)

End of

mRNA

(3 end)

An mRNA molecule is generally translated simultaneously

by several ribosomes in clusters called polyribosomes.

LE 17-20b

Ribosomes

mRNA

This micrograph shows a large polyribosome in a prokaryotic cell (TEM).

m0.1 m

LE 17-21

Ribosomes

mRNA

Signal

peptide

Signal-

recognition

particle

(SRP)SRP

receptor

protein

CYTOSOL

ER LUMEN Translocation

complex

Signal

peptide

removed

ER

membrane

Protein

LE 17-22

RNA polymerase

DNA

Polyribosome

RNA

polymerase

Direction of

transcription

mRNA

0.25 m

DNA

Polyribosome

Polypeptide

(amino end)

Ribosome

mRNA (5 end)

m

Las bases moleculares de la enfermedad anemia falciforme

Hemoglobina DNA normal

mRNA

3 5 53

5 3 35

Hemoglobina DNA mutante

mRNA

Hemoglobina normal Sickle-cell hemoglobin

Cualquier cambio en la secuencia de los nucleótidos del ADN se denomina

MUTACION

substitucion par-base

No afecta la secuencia de aminoacidos

U en lugar de C

Missense

A en lugar de G

NonsenseU en lugar de A

Stop

Amino terminal

Proteina

5 3

Carboxyl terminal

Stop

Stop

Stop

mRNA

normal

Insercion o perdida de un par -base

Frameshift causing immediate nonsense

Extra U

Missing

Frameshift causing

extensive missense

Insertion or deletion of 3 nucleotides:

no frameshift but extra or missing amino acid

Missing

Stop

Stop

Amino terminal Carboxyl terminal

Stop

Wild type

mRNA

Protein

5 3

TRANSCRIPTION

RNA PROCESSING

RNAtranscript

5

Exon

NUCLEUS

FORMATION OFINITIATION COMPLEX

CYTOPLASM

3

DNA

RNApolymerase

RNA transcript(pre-mRNA)

Intron

Aminoacyl-tRNAsynthetase

Aminoacid

tRNA

AMINO ACID ACTIVATION

3

mRNA

A

P

E Ribosomalsubunits

5

Growingpolypeptide

E A

Activatedamino acid

Anticodon

TRANSLATION

Codon

Ribosome