transcription translation

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TRANSCRIPTION TRANSLATION

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Transcription Translation. Gene expression. - process by which DNA directs protein synthesis two stages :. transcription and translation. Figure 14.UN01. Central Dogma. Protein. RNA. DNA. Gene expression. Differences Between DNA and RNA. Prokaryotes. Figure 14.4a-2. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Transcription Translation

TRANSCRIPTION TRANSLATION

Page 2: Transcription Translation

GENE EXPRESSION-process by which DNA directs protein synthesis two stages:

transcription and translation

Page 3: Transcription Translation

CENTRAL DOGMA

Gene expression

DNA RNA Protein

Page 4: Transcription Translation

DIFFERENCES BETWEEN DNA AND RNA

Page 5: Transcription Translation

PROKARYOTEStranslation of mRNA can begin before transcription has finished

FIGURE 14.4A-2

mRNA

DNATRANSCRIPTION

TRANSLATION

Polypeptide

Ribosome

(a) Bacterial cell

Page 6: Transcription Translation

EUKARYOTES-the nuclear envelope

separates transcription from translation; mRNA must be transported out of the nucleus to be translated

Eukaryotic RNA transcripts are modified through RNA processing to yield the finished mRNA

FIGURE 14.4B-3

Nuclearenvelope

Pre-mRNA

mRNA

DNA

RNA PROCESSING

TRANSCRIPTION

TRANSLATION

Polypeptide

Ribosome

(b) Eukaryotic cell

Overview:http://www.pbslearningmedia.org/asset/lsps07_int_celltrans/

Page 7: Transcription Translation

FIGURE 14.5

DNAtemplatestrand

Protein

mRNA

3

Trp

TRANSCRIPTION

TRANSLATION

Amino acid

Codon

5

35

3

5

Phe Gly Ser

GU G U UU G G UC C A

CA C A AA C C AG G T

GT G T TT G G TC C A

Page 8: Transcription Translation

GENETIC CODE

FIGURE 14.6

UUU

Second mRNA base

UUC

UUA

UUG

UCU

UCC

UCA

UCG

UAU

UAC

UAA

UAG

UGU

UGC

UGA

UGG

CUU

CUC

CUA

CUG

CCU

CCC

CCA

CCG

CAU

CACCAA

CAG

CGU

CGCCGA

CGG

AUU

AUC

AUA

AUG

ACU

ACC

ACA

ACG

AAU

AAC

AAA

AAG

AGU

AGC

AGA

AGG

GUU

GUC

GUA

GUG

GCU

GCC

GCA

GCG

GAU

GACGAA

GAG

GGU

GGCGGA

GGG

Firs

t mR

NA

base

(5

end

of c

odon

)

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

U

C

A

G

U C A G

Phe

LeuSer

Tyr Cys

Trp

Met orstart

Stop

Stop Stop

ArgGln

His

ProLeu

Val Ala

Asp

GluGly

IIeThr

Lys

Asn

Arg

Ser

Third

mR

NA

base

(3

end

of c

odon

)

64 codons; 20 amino acids

The genetic code is redundant: more than one codon may specify a particular amino acid

Page 9: Transcription Translation

UNIVERSAL GENETIC CODEFIGURE 14.7

(a) Tobacco plant expressinga firefly gene

(b) Pig expressing a jellyfishgene

Page 10: Transcription Translation

FIGURE 14.10

Nontemplate strand of DNA

Direction of transcription

RNA polymerase

3

53

5

RNA nucleotides

Template strand of DNA

Newly made RNA

3 end

5

UC

U

G

A

A

A

A

AA

A

AA

A

T T T

TTT

T

CC

C

CCC C

G

GG

U

TRANSCRIPTION

RNA polymerase assembles 5’ to 3’

-can start a chain without a primer

Page 12: Transcription Translation

EUKARYOTESFIGURE 14.9

Transcription factors

TATA box

Promoter Nontemplate strand

Start point

Transcriptioninitiationcomplex forms.

Transcription initiation complex

DNA

RNA transcript

A eukaryoticpromoter

Several transcriptionfactors bind to DNA.

35

5 3 35

35

35

3

2

1Template

strand

Transcription factors

RNA polymerase II

35

35 TA T A A A A

ATA T T T T

Transcription factors mediate the binding of RNA polymerase and the initiation of transcription

Page 13: Transcription Translation

EUKARYOTIC CELLS MODIFY RNA AFTER TRANSCRIPTION

FIGURE 14.UN03

DNA

Pre-mRNA

mRNA

Ribosome

Polypeptide

TRANSLATION

TRANSCRIPTION

RNA PROCESSING

Page 14: Transcription Translation

RNA PROCESSING

Protein-coding segmentPolyadenylation

signal

G P

A modified guaninenucleotide added tothe 5 end

50–250 adeninenucleotides added to the 3 end

35

5 Cap 5 UTR 3 UTR Poly-A tailStartcodon

Stopcodon

P P AAUAAA …AAA AAA

Modifications:• The 5 end receives a modified G nucleotide 5 cap• The 3 end gets a poly-A tail

Functions:• Facilitating the export of mRNA to the cytoplasm• Protecting mRNA from hydrolytic enzymes• Helping ribosomes attach to the 5 end

Page 15: Transcription Translation

ALTERNATIVE RNA SPLICING

FIGURE 14.12

Introns cut out andexons spliced together

31–104

5 Cap

5 UTR 3 UTR

Poly-A tail

Codingsegment

1–146

AAUAAA

105– 146

5 Cap Poly-A tail1–30

mRNA

Pre-mRNAIntron Intron

RNA splicing removes introns (noncoding) and joins exons (translates to amino acids), creating an mRNA molecule with a continuous coding sequence

Page 16: Transcription Translation

TRANSLATION

FIGURE 14.14

5

tRNA

Polypeptide

Ribosome

Anticodon

mRNA

Codons 3

tRNA withamino acidattached

Amino acids

Gly

Trp

Phe

A A A

A C CC

CG

U U U G G CU G G

A cell translates an mRNA message into protein with the help of transfer RNA (tRNA)

Page 17: Transcription Translation

TRNAFIGURE 14.15

5

Anticodon

3

Amino acidattachment site

AnticodonAnticodon

A A G53

Hydrogenbonds

53

Amino acidattachment site

Hydrogenbonds

A

A

G

A

CG

CC

C

C

UA

C G

UU

AA A

A

C

G U

A

C G U

A

C

GU

AC

G

U

*

CG

*

G

GU

A

AA

A

C C

C

CC

GGGG

G

UUU

U

GG

G

G

A

A

* *

*

*

*

*

**

*

(b) Three-dimensional structure

(c) Symbol used in this book(a) Two-dimensional structure

*

Page 18: Transcription Translation

FIGURE 14.17

PE A

tRNAmolecules

A

Largesubunit

Smallsubunit

Growing polypeptide Exit tunnel

E P

mRNA5 3

Growing polypeptide(a) Computer model of functioning ribosome

tRNA

5

3E

mRNA

(c) Schematic model with mRNA and tRNA

Codons

Amino end Next amino acidto be added to

polypeptidechain

Largesubunit

Smallsubunit

A site (Aminoacyl-tRNA binding site)

P site (Peptidyl-tRNA binding site)

Exit tunnel

E site (Exit site)

mRNA binding site

(b) Schematic model showing binding sites

RIBOSOME STRUCTURE

Page 20: Transcription Translation

FIGURE 14.19-3 Amino endof polypeptide

mRNARibosome ready fornext aminoacyl tRNA P

site

P i

5

3E

GTP

Asite

GDP

Peptide bondformation

Codon recognition

Translocation

E

P A

E

P A

P i

GTP

GDP

E

P A

32

1

ELONGATION

Page 21: Transcription Translation

TERMINATIONFIGURE 14.20-3

Freepolypeptide

Ribosome reaches astop codon on mRNA.

5

3

2 GTP

2 GDP P i

Releasefactor

Stop codon(UAG, UAA, or UGA)

5

35

3

Ribosomalsubunits and othercomponentsdissociate.

Release factorpromoteshydrolysis.

2 31

Page 22: Transcription Translation

POLYRIBOSOMES

FIGURE 14.22

Incomingribosomalsubunits

(b) A large polyribosome in a bacterialcell (TEM)

Ribosomes

mRNA

(a) Several ribosomes simultaneously translating onemRNA molecule

0.1 m

Start of mRNA(5 end)

End of mRNA(3 end)

Growingpolypeptides

Completedpolypeptide

Polyribosome

A number of ribosomes can translate a single mRNA molecule simultaneously

Page 23: Transcription Translation

REVIEW

FIGURE 14.24

A

U A

tRNA

5 Cap

3

mRNA

Ribosomalsubunits

Aminoacyl(charged)tRNA

PE

G

5

3

Ribosome

Codon

Anticodon

TRANSLATION

Aminoacid

Aminoacyl-tRNAsynthetase

CYTOPLASM

NUCLEUS

AMINO ACIDACTIVATION

Intron

5 Cap

Poly-A

TRANSCRIPTION

RNAPROCESSING

RNAtranscript

RNA transcript(pre-mRNA)

RNApolymerase

Exon

DNA

Poly-A

Poly-A

U GUG U UA A A

A C C UA

CAE

http://www.pbslearningmedia.org/asset/lsps07_int_celltrans/