RNA ANDRNA AND PROTEIN SYNTHESIS PROTEIN SYNTHESIS

How your cell makes very How your cell makes very important proteinsimportant proteins

• The production (synthesis) of proteinsproteins.

• 3 phases3 phases:

1.1. TranscriptionTranscription

2.2. RNA processingRNA processing

3.3. TranslationTranslation

• DNA DNA RNA RNA ProteinProtein

DNA DNA RNA RNA ProteinProtein

Nuclearmembrane

TranscriptionTranscription

RNA ProcessingRNA Processing

TranslationTranslation

DNA

Pre-mRNA

mRNA

Ribosome

Protein

Eukaryotic Eukaryotic CellCell

Before making proteins, Your Before making proteins, Your cell must first make RNAcell must first make RNA

• Question:Question:

• How does RNARNA (ribonucleic acid) (ribonucleic acid) differ from DNA (deoxyribonucleic acid)DNA (deoxyribonucleic acid)?

RNARNA differs from DNADNA

1. RNARNA has a sugar ribosesugar ribose

DNADNA has a sugar deoxyribosesugar deoxyribose

2. RNARNA contains uracil (U)uracil (U)

DNADNA has thymine (T)thymine (T)

3. RNARNA molecule is single-strandedsingle-stranded

DNADNA is double-strandeddouble-stranded

1. Transcription1. Transcription

• Then moves along one of the DNA strandsDNA strands and links RNARNA nucleotides together.

Nuclearmembrane

TranscriptionTranscription

RNA ProcessingRNA Processing

TranslationTranslation

DNA

Pre-mRNA

mRNA

Ribosome

Protein

Eukaryotic Eukaryotic CellCell

1. Transcription OR1. Transcription OR RNA production RNA production

• RNA molecules are produced by copying part of DNA into a complementary sequence of RNA

• This process is started and controlled by an enzyme called RNA polymerase.

1. Transcription1. Transcription

DNADNA

pre-mRNApre-mRNA

RNA PolymeraseRNA Polymerase

Question:Question:

• What would be the complementary RNARNA strand for the following DNADNA sequence?

• DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’

Types of RNATypes of RNA

• Three types ofThree types of RNARNA:

A.A. messenger RNA (mRNA)messenger RNA (mRNA)

B.B. transfer RNA (tRNA)transfer RNA (tRNA)

C.C. ribosome RNA (rRNA)ribosome RNA (rRNA)

• Remember: all produced in theRemember: all produced in the nucleusnucleus!!

mRNA

• Carries instructions from DNA to the rest of the ribosome.

• Tells the ribosome what kind of protein to make

• Acts like an email from the principal to the cafeteria lady.

A. Messenger RNA (mRNA)A. Messenger RNA (mRNA)

methionine glycine serine isoleucine glycine alanine stopcodon

proteinprotein

A U G G G C U C C A U C G G C G C A U A AmRNAmRNA

startcodon

Primary structure of a proteinPrimary structure of a protein

aa1 aa2 aa3 aa4 aa5 aa6

peptide bonds

codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1

If the cell is a school…If the cell is a school…

• The Nucleus is the school officeThe Nucleus is the school office• The Nucleolus is the principal’s The Nucleolus is the principal’s

officeoffice• The DNA is the principalThe DNA is the principal• Ribosomes are the cafeteria ladiesRibosomes are the cafeteria ladies• mRNA is the email from the mRNA is the email from the

principal to the cafeteria ladyprincipal to the cafeteria lady

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

rRNA

• Part of the structure of a ribosome

• Helps in protein production

tRNA

A go-getter. Gets the right parts to make the right protein according to mRNA instructions

B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)

amino acidamino acidattachment siteattachment site

U A C

anticodonanticodon

methionine amino acidamino acid

2. RNA Processing2. RNA Processing

Nuclearmembrane

TranscriptionTranscription

RNA ProcessingRNA Processing

TranslationTranslation

DNA

Pre-mRNA

mRNA

Ribosome

Protein

Eukaryotic Eukaryotic CellCell

2. RNA Processing2. RNA Processing

• IntronsIntrons are pulled out and exonsexons come together.

• End product is a mature RNA mature RNA moleculemolecule that leaves the nucleusnucleus to the cytoplasm.cytoplasm.

• Introns bad…… Exons good!Introns bad…… Exons good!

2. RNA Processing2. RNA Processing

pre-RNA molecule

intron

intronexon exon exon

exon exon exon

Mature RNA moleculeMature RNA molecule

exon exon exon

intron intron

splicesome splicesome

RibosomesRibosomes

PSite

ASite

Largesubunit

Small subunit

mRNAmRNA

A U G C U A C U U C G

3. Translation - making 3. Translation - making proteinsproteins

Nuclearmembrane

TranscriptionTranscription

RNA ProcessingRNA Processing

TranslationTranslation

DNA

Pre-mRNA

mRNA

Ribosome

Protein

Eukaryotic Eukaryotic CellCell

3. Translation3. Translation

• Three parts:

1. initiationinitiation: start codon (AUG)

2. elongationelongation:

3. terminationtermination: stop codon (UAG)

• Let’s make a PROTEIN!!!!PROTEIN!!!!.

3. Translation3. Translation

PSite

ASite

Largesubunit

Small subunit

mRNAmRNA

A U G C U A C U U C G

InitiationInitiation

mRNAmRNA

A U G C U A C U U C G

2-tRNA

G

aa2

A U

A

1-tRNA

U A C

aa1

anticodon

hydrogenbonds codon

mRNAmRNA

A U G C U A C U U C G

1-tRNA 2-tRNA

U A C G

aa1 aa2

A UA

anticodon

hydrogenbonds codon

peptide bond

3-tRNA

G A A

aa3

ElongationElongation

mRNAmRNA

A U G C U A C U U C G

1-tRNA

2-tRNA

U A C

G

aa1

aa2

A UA

peptide bond

3-tRNA

G A A

aa3

Ribosomes move over one codon

(leaves)

mRNAmRNA

A U G C U A C U U C G

2-tRNA

G

aa1

aa2

A UA

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

mRNAmRNA

A U G C U A C U U C G

2-tRNA

G

aa1aa2

A U

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

(leaves)

Ribosomes move over one codon

mRNAmRNA

G C U A C U U C G

aa1aa2

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

U G A

5-tRNA

aa5

mRNAmRNA

G C U A C U U C G

aa1aa2

A

peptide bonds

3-tRNA

G A A

aa3

4-tRNA

G C U

aa4

A C U

U G A

5-tRNA

aa5

Ribosomes move over one codon

mRNAmRNA

A C A U G U

aa1

aa2

U

primaryprimarystructurestructureof a proteinof a protein

aa3

200-tRNA

aa4

U A G

aa5

C U

aa200

aa199

terminatorterminator or stopor stop codoncodon

TerminationTermination

End ProductEnd Product• The end products of protein synthesis is

a primary structure of a proteinprimary structure of a protein.

• A sequence of amino acid amino acid bonded together by peptide bondspeptide bonds.

aa1

aa2 aa3 aa4aa5

aa200

aa199

Question:Question:

• The anticodon The anticodon UACUAC belongs to a belongs to a tRNAtRNA that that recognizes and binds to a particular recognizes and binds to a particular amino amino acidacid..

• What would be the What would be the DNA base code DNA base code for this for this amino acid?amino acid?

Answer:Answer:

• tRNA tRNA - UAC (anticodon)- UAC (anticodon)

• mRNAmRNA - AUG (codon)- AUG (codon)

• DNA DNA - TAC- TAC