Adn Arn Procesos Sdbhs Xmo 2012

7/27/2019 Adn Arn Procesos Sdbhs Xmo 2012

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1. ADN, ARN structure

2. ADN replication

3. Transcription, translation



Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• 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)




• El ADN tiene cuatro tipos de bases, A, T, C y G

PIRIMIDINAS

TIMINA (T) CITOSINA (C)

PURINAS

ADENINA (A) GUANINA (G)




• 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)




• James Watson and Francis Crick worked outthe three-dimensional structure of ADN, basedon work by Rosalind Franklin

ADN is a double-stranded helix




• 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



• 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



• 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



• 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





– 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



Transcription produces genetic messages in theform of mARN

Figure 10.9A

ARNpolymerase

ARN nucleotide

Direction of transcription

Newly made ARN

Templatestrand of ADN




• 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




ARN transcripts of ADN




• 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




• 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




ADN molecule

Gene 1

Gene 2

Gene 3

ADN strand

TRANSCRIPTION

ARN

Polypeptide

TRANSLATION Codon

Amino acid



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”




• An exercise in translating the genetic code

Startcodon

ARN

Transcribed strand

StopcodonTranslation

Transcription

ADN

Polypeptide




• 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




• Each tARN molecule has a triplet anticodon onone end and an amino acid attachment site on

the other

Anticodon

Amino acidattachmentsite




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




An initiation codon marks the start of anmARN message

End

Start of genetic message

AUG = methionine




• mARN, a specific tARN, and the ribosomesubunits assemble during initiation

1

Initiator tARN

mARN

Startcodon Small ribosomal

subunit

2

P site

Largeribosomalsubunit

A site




• 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




1 Codon recognition

Amino acid

Anticodon

AsiteP site

Polypeptide

2 Peptide bondformation

3 Translocation

Newpeptidebond

mARNmovement

mARN

Stopcodon



ba

Red object = ?

What molecules are present

in this photo?

Tipos de ARN



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




• 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




• 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




Normal hemoglobin ADN

mARN

Normal hemoglobin

Glu

Mutant hemoglobin ADN

mARN

Sickle-cell hemoglobin

Val




• 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




Deletion

Duplication

Inversion

Homologouschromosomes

Reciprocaltranslocation

Nonhomologouschromosomes

•Chromosomal changes can be large or small




• 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



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

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Adn Arn Procesos Sdbhs Xmo 2012