BELLRINGER!! Describe One differences between DNA &

RNA.1.Recall from reading

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OBJECTIVES Compare DNA to RNA

StructuresProtein Synthesis

Three types are RNA

How do we get from How do we get from DDNNAA to to ProteinsProteins??

From nucleus to cytoplasm…• Where are the genes?

– genes are on chromosomes in nucleus

• Where are proteins synthesized?– proteins made in cytoplasm by

ribosomes

• How does the information get from nucleus to cytoplasm?

RNA

nucleus

Why would RNA be useful in a cell?

DNA is the MASTER PLAN

RNA is the copy of the master plan

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Since DNA can’t leave the nucleus, we need something to carry the message to the ribosomes

RNA

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RNA is similar to DNA EXCEPT:

SINGLE strand

URACIL (not thymine)

RIBOSE

DOUBLE strand

DEOXYRIBOSE

A C G T

RNA DNAStructure

Sugar

Base

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Structure of RNAStructure of RNA

Pair the RNA BASES! G=CC=GT=AA=U

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.

Three Types of RNAThree Types of RNA Messenger RNA (mRNA)Messenger RNA (mRNA)

Ribosomal RNA (rRNA)Ribosomal RNA (rRNA)

Transfer RNA (tRNA)Transfer RNA (tRNA)

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Messenger RNA mRNA- Copies DNA’s code & carries mRNA- Copies DNA’s code & carries

the genetic information to the the genetic information to the ribosomesribosomes

Single, straight strand of nucleotides

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Ribosomal RNARibosomal RNA rRNA-binds to the rRNA-binds to the

mRNA and assemble mRNA and assemble the amino acids in the the amino acids in the correct ordercorrect order

2 subunits:2 subunits: LargeLarge smallsmall

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Transfer RNATransfer RNA tRNA- transfers amino acids to the tRNA- transfers amino acids to the

ribosomesribosomes where proteins are where proteins are synthesizedsynthesized

Clover-leaf shapeOne end carries the amino acid;

Opposite end has three nucleotide bases

called the anticodon

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Objectives Describe the three step process

InitiationElongationTermination

DNA

mRNA

Transcription

Introduction

The Central Dogma of Molecular Biology

Cell

Polypeptide(protein)

TranslationRibosome

Protein Synthesis Flow of Information: DNA RNA Proteins Transcription Translation

Transcription is the process by which a molecule of DNA is copied into a complementary Strand strand of RNA.

nucleus

Transcription

DNA

(mRNA) carries the code

(tRNA) brings in amino acids

RNA

(rRNA)makes aribosome

cytoplasm

Translation

DNA

RNA

Proteins Amino acid

chain folds into a

functional protein

http://www.youtube.com/watch?v=ztPkv7wc3yU&feature=related

BELLRINGER!! Transcription: Write the complimentary RNA strand

DNA: GATACGGCAATTACRNA:

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TranscriptionTranscription: the synthesis of mRNA from a

DNA templatemRNA, rRNA, and tRNA must all be

transcribed for protein synthesis to take place

**Only ONE strand will be transcribed

STEP 1: DNA strands separate

RNA POLYMERASE (RP) recognizes a promoter on the DNA sequence

PROMOTER: base sequence that signals the start of a gene

DNA is split by RP and one strand is used as a template

RN

A

Pol

ymer

ase

- brings in complimentary RNA nucleotide to base pair with DNA

**Same process as replication EXCEPT only 1 strand is copied, and U replaces T

Elongation: RNA Polymerase

A UG

RNA

C U U G

GC

RN

A

Pol

ymer

ase

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Remember the Remember the Complementary Complementary

BasesBasesOn DNA:

A-T C-G

On RNA: A-U C-G

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Question:Question:What would be the What would be the complementary RNA strand complementary RNA strand for the following DNA for the following DNA sequence?sequence?

DNA 5’-DNA 5’-GATACGTATGGATACGTATG-3’-3’

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Answer:Answer:DNA 5’-DNA 5’-GATACGTATG-3’GATACGTATG-3’

RNA 3’-RNA 3’-CUAUGCAUAC-5’CUAUGCAUAC-5’

Termination: the process continues until RNA polymerase reaches a termination signal in the DNA which indicates the end of a gene

Objections Describe the three steps in Translation

Translate mRNA codons into amino acids

Translation makes

Proteins from RNA

Reading the DNA codeEvery 3 DNA bases pairs with 3 mRNA basesEvery group of 3 mRNA bases encodes a

single amino acidCodon- coding triplet of mRNA bases

U C A G

U

C

A

G

GACU

GACU

GACU

GACU

UUUUUCUUAUUG

CUUCUCCUACUG

AUUAUCAUAAUG

GUUGUCGUAGUG

phe

leu

leu

ile

met (start)

val

UCUUCCUCAUCG

CCUCCCCCACCG

ACUACCACAACG

GCUGCCGCAGCG

ser

pro

thr

ala

UAUUACUAAUAG

CAUCACCAACAG

AAUAAC

AAGAAA

GAUGACGAAGAG

tyr

stopstop

his

gln

asn

lys

asp

glu

UGUUGCUGAUGG

CGUCGCCGACGG

AGUAGCAGAAGG

GGUGGCGGAGGG

cys

stoptrp

arg

ser

arg

gly

Firs

t B

ase

Third

Base

Second Base

Virtually all organisms share the same genetic code “unity of life”

Initiation mRNA binds with

the ribosome.

A “start” codon (AUG) on mRNA signals the beginning of a protein chain.

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Happens at RibosomesHappens at Ribosomes•Ribosomes read mRNA three bases (1 codon) at a time and construct the proteins

Figure 10.14

1 Codon recognition

Amino acid

Anticodon

AsiteP site

Polypeptide

2 Peptide bond formation

3 Translocation

Newpeptide

bond

mRNAmovement

mRNA

Stopcodon

ElongationmRNA is on a ribosome with the

start codon AUGA tRNA with anticodon UAC can now bind

to mRNA because bases match up.Peptide bonds join the amino

acidsRibosome moves over one codonThe process repeats until…….

Codons and AnticodonsThe 3 bases of an anticodon are complementary to the 3 bases of a codon

MET-tRNA

codon codon codon

mRNA

anticodon

Elongation

The mRNA moves a codon at a time relative to the ribosomeA tRNA pairs with each codon, adding an amino

acid to the growing polypeptideA STOP codon causes the mRNA-ribosome

complex to fall apart

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Step 3: Termination

Occurs when a stop codon is reachedThe string of amino acids (polypeptide) is

releasedSubunits break apart.

Translationhttp://www.youtube.com/watch?v=-zb6r1MM

Tkc&feature=related

tRNA FunctionAmino acids must be in the correct order for

the protein to function correctlytRNA lines up amino acids using mRNA code

Ribosomes build polypeptides

Figure 10.12A-C

Codons

tRNAmolecules

mRNA

Growingpolypeptide

Largesubunit

Smallsubunit

mRNA

mRNAbinding

site

P site A site

P A

Growingpolypeptide

tRNA

Next amino acidto be added to

polypeptide

Click image to view movie

Translating the message into Protein

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End Product –The Protein!End Product –The Protein!The end products of protein

synthesis is a primary structure of a protein

A sequence of amino acid bonded together by peptide bonds

Met

aa2 aa3 aa4aa5

aa200

aa199

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For ALL life!strongest support for a common origin for all life

An amino acid may have more than one codon, but each codon makes only ONE amino acidThere is also:

1 start codon (AUG = methionine)

and 3 stop codons.

How are the codons matched to amino acids?

TACGCACATTTACGTACGCGGDNA

AUGCGUGUAAAUGCAUGCGCCmRNA

aminoacid

tRNA

anti-codon

codon

5' 3'

3' 5'

3' 5'

UAC

MetGCA

ArgCAU

Val

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• Translation is the process of decoding the mRNA into a polypeptide (amino acid) chain

Transcription

Codon Codon Codon

Translation

DNA

T T C A G T C A G

DNAtemplatestrand

mRNA

A A G U C A G U C MessengerRNA

Protein Lysine Serine ValinePolypeptide(amino acidsequence)

Translation

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Transcription vs. Translation ReviewTranscription

Process by which genetic information encoded in DNA is copied onto messenger RNA

Occurs in the nucleus

DNA mRNA

TranslationProcess by which

information encoded in mRNA is used to assemble a protein at a ribosome

Occurs on a Ribosome

mRNA protein