Transcript
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
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
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
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 17-16
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 17-21
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
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