Adn Arn Procesos Sdbhs Xmo 2012
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Transcript of Adn Arn Procesos Sdbhs Xmo 2012
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1. ADN, ARN structure
2. ADN replication
3. Transcription, translation
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• El ADN es un ácido nucleico, formado por una cadena
larga de nucleótidos.
El ADN y el ARN son polímeros de nucleótidos
Nucleótido
Grupo fosfato
Basenitrogenada
Azúcar
Polinucleótido Estructura azúcar-fosfato
Nucleótido de ADN
Grupofosfato
Bases nitrogenadas(A, G, C, o T)
TIMINA (T)
AZúCAR(deoxirribosa)
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• El ADN tiene cuatro tipos de bases, A, T, C y G
PIRIMIDINAS
TIMINA (T) CITOSINA (C)
PURINAS
ADENINA (A) GUANINA (G)
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• El ARN también es un ácido nucleico
– su azúcar es diferente (ribosa)
–
la base Timina se sustituye con Uracilo – usualmente es de una fibra sencilla
GRUPO FOSFATO
BASE NITROGENADA(A, G, C, o U)
Uracilo (U)
AZÚCAR(ribosa)
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• James Watson and Francis Crick worked outthe three-dimensional structure of ADN, basedon work by Rosalind Franklin
ADN is a double-stranded helix
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• Los enlaces de hidrógeno entre las bases las
mantienen unidas según el patrón de A y T, C y G
Modelo de cintas Estructura química parcial Modelo computacional
Enlaces de hidrógeno
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Desenredado y duplicación del ADN, cada extremo o fibra
de la hélice es el molde para una nueva fibra o hilo.
helicasa
ADN polimerasa
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• ADN replication begins at many specific sites
How can entire chromosomes be replicated during S phase?
Figure 10.5A
Parental strandOrigin of replication
Bubble
Two daughter ADN molecules
Daughter strand
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• Each strand of thedouble helix is
oriented in theopposite direction
Figure 10.5B
5 end 3 end
3 end 5 end
P
P
P
P
P
P
P
P
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• ADNpolymerase
works inonly onedirection
5 end
P
P
Parental ADN
ADN polymerasemolecule
5 3
3 5
3 5
Daughter strandsynthesizedcontinuously
Daughter strandsynthesizedin pieces
ADN ligase
Overall direction of replication
5 3
• Telomeresequencesare lost with eachreplication.
• Cancer,aging
telomeres
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– The ADN is transcribed into ARN, which istranslated into the polypeptide
ADN
ARN
Protein
TRANSCRIPTION
TRANSLATION
• The information constituting an organism’sgenotype is carried in its sequence of bases
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Transcription produces genetic messages in theform of mARN
Figure 10.9A
ARNpolymerase
ARN nucleotide
Direction of transcription
Newly made ARN
Templatestrand of ADN
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• In transcription, ADN helix unzips
– ARN nucleotides lineup along one strandof ADN, following the
base-pairing rules
– single-strandedmessenger ARN peels
away and ADNstrands rejoin
ARN polymerase
ADN of gene
Promoter ADN Terminator
ADNInitiation
Elongation
Termination
Area shownin Figure 10.9A
GrowingARN
ARN
polymerase
Completed ARN
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ARN transcripts of ADN
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• Noncodingsegments,introns, arespliced out
• A cap and a tailare added tothe ends
Eukaryotic ARN is processed before leavingthe nucleus
ADN
ARNtranscriptwith capand tail
mARN
Exon Intron IntronExon Exon
TranscriptionAddition of cap and tail
Introns removed
Exons spliced together
Coding sequence
NUCLEUS
CYTOPLASM
Tail
Cap
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• The “words” of the ADN “language” are tripletsof bases called codons
– The codons in a gene specify the amino acid
sequence of a polypeptide
Translation of nucleic acids into amino acids
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ADN molecule
Gene 1
Gene 2
Gene 3
ADN strand
TRANSCRIPTION
ARN
Polypeptide
TRANSLATION Codon
Amino acid
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U C A G
U
C
A
G
G
A
CU
G
A
CU
G
A
C
U
GA
C
U
UUU UUC
UUA
UUG
CUU
CUC
CUA CUG
AUU
AUC
AUA
AUG
GUU GUC
GUA
GUG
phe
leu
leu
ile
met (start)
val
UCU UCC
UCA
UCG
CCU
CCC
CCA CCG
ACU
ACC
ACA
ACG
GCU GCC
GCA
GCG
ser
pro
thr
ala
UAU UAC
UAA
UAG
CAU
CAC
CAA CAG
AAU
AAC
AAG
AAA
GAU GAC
GAA
GAG
tyr
stop
stop
his
gln
asn
lys
asp
glu
UGU UGC
UGA
UGG
CGU
CGC
CGA CGG
AGU
AGC
AGA AGG
GGU GGC
GGA
GGG
cys
stop
trp
arg
ser
arg
gly
F i r s t B a s
eTh i r d
B a s e
Second Base
Virtually all organisms share the same genetic code
“unity of life”
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• An exercise in translating the genetic code
Startcodon
ARN
Transcribed strand
StopcodonTranslation
Transcription
ADN
Polypeptide
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• In the cytoplasm, aribosome attachesto the mARN andtranslates its
message into apolypeptide
• The process is aided
by transfer ARNs
Transfer ARN molecules serve as interpretersduring translation
Hydrogen bond
Amino acid attachment site
ARN polynucleotide chain
Anticodon
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• Each tARN molecule has a triplet anticodon onone end and an amino acid attachment site on
the other
Anticodon
Amino acidattachmentsite
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Ribosomes build polypeptides
Codons
tARNmolecules
mARN
Growingpolypeptide
Large
subunit
Smallsubunit
mARN
mARNbindingsite
P site A site
P A
Growingpolypeptide
tARN
Next amino acidto be added topolypeptide
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An initiation codon marks the start of anmARN message
End
Start of genetic message
AUG = methionine
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• mARN, a specific tARN, and the ribosomesubunits assemble during initiation
1
Initiator tARN
mARN
Startcodon Small ribosomal
subunit
2
P site
Largeribosomalsubunit
A site
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• The mARN moves a codon at a time relative tothe ribosome
– A tARN pairs with each codon, adding an aminoacid to the growing polypeptide
– A STOP codon causes the mARN-ribosome
complex to fall apart
Elongation
Amino acid
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1 Codon recognition
Amino acid
Anticodon
AsiteP site
Polypeptide
2 Peptide bondformation
3 Translocation
Newpeptidebond
mARNmovement
mARN
Stopcodon
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ba
Red object = ?
What molecules are present
in this photo?
Tipos de ARN
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Tipos de ARN
Tipo de ARN Ubicación Función
ARN mensajero(mARN)
Núcleo,migra a losribosomasen elcitoplasma
Lleva lasecuencia de lainformación delADN a losribosomas
ARN detransferencia(tARN)
Citoplasma Provee unenlaceentre el mARN
y losaminoácidos;transfiereaminoácidos alos ribosomas
ARN ribosomal(rARN)
Citoplasma Componenteestructural de losribosomas
R i Th fl f ti i f ti i th ll
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• The sequence of codons in ADN spells out theprimary structure of a polypeptide
– Polypeptides form proteins that cells and
organisms use
Review: The flow of genetic information in the cellis ADNARNprotein
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• Mutations are changes in the ADN basesequence
– caused by errors in ADN replication or by
mutagens– change of a single ADN nucleotide causes
sickle-cell disease
Mutations can change the meaning of genes
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Normal hemoglobin ADN
mARN
Normal hemoglobin
Glu
Mutant hemoglobin ADN
mARN
Sickle-cell hemoglobin
Val
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• Types of mutations
mARN
NORMAL GENE
BASE SUBSTITUTION
BASE DELETION
Protein Met Lys Phe Gly Ala
Met Lys Phe Ser Ala
Met Lys Leu Ala His
Missing
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Deletion
Duplication
Inversion
Homologouschromosomes
Reciprocaltranslocation
Nonhomologouschromosomes
•Chromosomal changes can be large or small
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• Summary of transcription
andtranslation
1Stage mARN is
transcribed from aADN template.
Anticodon
ADN
mARNARNpolymerase
TRANSLATION
Enzyme
Amino acid
tARN
Initiator tARN
Largeribosomal
subunit
Smallribosomalsubunit
mARN
StartCodon
2Stage Each aminoacid attaches to itsproper tARN with the
help of a specificenzyme and ATP.
3Stage Initiation of polypeptide synthesis
The mARN, the firsttARN, and theribosomal subunitscome together.
TRANSCRIPTION
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4Stage ElongationGrowingpolypeptide
Codons
5Stage Termination
mARN
Newpeptidebondforming
Stop Codon
The ribosome recognizes
a stop codon. The poly-peptide is terminated andreleased.
A succession of tARNsadd their amino acids tothe polypeptide chain asthe mARN is movedthrough the ribosome,one codon at a time.
Polypeptide