Protein SynthesisProtein Synthesis

DNA’s destiny!DNA’s destiny!

Protein ReviewProtein Review

• Long chains Long chains ((POLYPEPTIDESPOLYPEPTIDES) ) formed by 20 different formed by 20 different amino acidsamino acids

• Protein Protein shapeshape is is determined by determined by DNA DNA sequence!sequence!

SO HOW DO WE GO SO HOW DO WE GO FROM DNA TO FROM DNA TO

PROTEIN??PROTEIN??

POLYPEPTIDE MADEPOLYPEPTIDE MADEOF MANY AMINO ACIDSOF MANY AMINO ACIDS

What does DNA really do?What does DNA really do?• The genes in DNA must code for something The genes in DNA must code for something

right??? right??? So what IS IT????So what IS IT????

• The DNA alphabet (A, T, C, G) essentially The DNA alphabet (A, T, C, G) essentially codes for codes for amino acidsamino acids

– Which are the Which are the building blocksbuilding blocks for……. for…….

PROTEINS!!!!!!!!!!PROTEINS!!!!!!!!!!

What does DNA do?? Con’t……What does DNA do?? Con’t……

• The The orderorder of of basesbases in in DNADNA contains contains a code for a a code for a SPECIFICSPECIFIC order of order of amino acidsamino acids

• The The orderorder of of amino acidsamino acids determines the determines the shapeshape and and functionfunction of the of the proteinprotein

DNA to Protein overviewDNA to Protein overviewDNADNA

mRNAmRNA

RibosomeRibosome““reads” mRNAreads” mRNA

tRNA brings proper AMINO ACIDS to ribosome as mRNA is readtRNA brings proper AMINO ACIDS to ribosome as mRNA is read

Amino acids are linked together to make PROTEIN that gene coded forAmino acids are linked together to make PROTEIN that gene coded for

TAKES TAKES PLACE IN PLACE IN NUCLEUSNUCLEUS

TAKES PLACE TAKES PLACE IN IN

CYTOPLASMCYTOPLASM

DNA to Protein Overview: DNA to Protein Overview: The 2 phasesThe 2 phases• PHASE 1:PHASE 1: In the In the NUCLEUSNUCLEUS

– Called Called TRANSCRIPTIONTRANSCRIPTION– ““TranscribingTranscribing” DNA to ” DNA to singlesingle strand of strand of mRNAmRNA– This creates a “This creates a “readablereadable” ” messagemessage for for ribosomesribosomes

• PHASE 2:PHASE 2: In the In the CYTOPLASMCYTOPLASM– Called Called TRANSLATIONTRANSLATION– RibosomesRibosomes “ “translatetranslate” the message found on the ” the message found on the

mRNAmRNA strand into strand into amino acidsamino acids– The The amino acidsamino acids are are strungstrung together to together to makemake the the

proteinprotein the gene coded for the gene coded for

DNA to PROTEIN DNA to PROTEIN

http://www.youtube.com/watch?v=983lhh20rGY

RNA BasicsRNA Basics

• RNARNA is is single single strandedstranded

• Contains Contains U (uracil)U (uracil) insteadinstead of T (thymine) of T (thymine)– So So AA binds with binds with UU in RNA in RNA

• Types of RNA:Types of RNA:– mRNAmRNA

• MessengerMessenger RNA RNA• Result of Result of transcriptiontranscription• Contains a Contains a messagemessage from DNA from DNA

– tRNAtRNA• TransferTransfer RNA RNA• Brings proper Brings proper amino acidamino acid to to ribosomeribosome during during translationtranslation

Phase 1: Transcription- Making Phase 1: Transcription- Making mRNAmRNA

Occurs Occurs INSIDE THE INSIDE THE NUCLEUSNUCLEUS

1.1. DNADNA strands strands separateseparate at the bases at the bases

2.2. ComplimentaryComplimentary RNA basesRNA bases take their places take their places along along oneone of the DNA strands with the help of of the DNA strands with the help of enzymesenzymes

– Remember…..RNARemember…..RNA bases are bases are A, C, G, and U A, C, G, and U (uracil)(uracil)

– U U insteadinstead of T! of T!– This This createscreates an an mRNA strandmRNA strand

Let’s see this in action!

Phase 1: Transcription con’t…Phase 1: Transcription con’t…Let’s practice making mRNA from a DNA strand!

T

A

C

T

T

A

G

A

T

A

U

G

A

A

U

C

U

A

DNA DNA StrandsStrands

A

T

G

A

A

T

C

T

A

mRNA mRNA StrandStrand

mRNA leaves nucleus mRNA leaves nucleus and attaches to a and attaches to a ribosome in the cytoplasmribosome in the cytoplasm

DNA IS UNZIPPEDDNA IS UNZIPPEDmRNA is constructed using mRNA is constructed using ONE strand of DNA. mRNA ONE strand of DNA. mRNA pairs U withpairs U withA, instead of T.A, instead of T.

Diagram of TranscriptionDiagram of Transcription

Phase 2: Translation- Making a Phase 2: Translation- Making a ProteinProtein

Occurs in the CYTOPLASM at a Occurs in the CYTOPLASM at a RIBOSOMERIBOSOME

1.1. mRNAmRNA from transcription from transcription leaves the leaves the nucleusnucleus

2.2. mRNAmRNA attachesattaches to a to a ribosomeribosome3.3. RibosomeRibosome “reads” the “reads” the messagemessage in the in the

mRNAmRNA• Ribosomes can only read Ribosomes can only read 3 bases3 bases at a at a

time!!!time!!!• 3 mRNA bases3 mRNA bases is called a is called a CODONCODON..

Translation con’t….Translation con’t….

4.4. Reading Reading mRNAmRNA by ribosome signals a by ribosome signals a tRNAtRNA to bring the correct to bring the correct amino acidamino acid

• A A codoncodon codes for codes for 1 amino acid1 amino acid (LOOK AT YOUR CODON SHEET)(LOOK AT YOUR CODON SHEET)

• Ex.Ex. AUGAUG codes for tRNA to bring codes for tRNA to bring MethionineMethionine

5.5. tRNA tRNA drops off amino acid at the drops off amino acid at the ribosomeribosome

Translation con’t….Translation con’t….

6.6. RibosomeRibosome “reads” the next “reads” the next codoncodon to to signal for the next signal for the next amino acidamino acid

7.7. Amino acidsAmino acids are connected by are connected by BONDSBONDS as they are brought by as they are brought by tRNAtRNA

8.8. The last The last codoncodon read is a read is a STOPSTOP codon that means the codon that means the proteinprotein is is complete!complete!

Translation DiagramTranslation Diagram

Forming PolypeptideForming Polypeptide

RibosomeRibosome

mRNAmRNA

Close up of translationClose up of translation

Let’s practice Translation!Let’s practice Translation!• The strand we made earlier The strand we made earlier

is:is:• If If 3 bases3 bases code for code for 1 1

amino acidamino acid, how many , how many amino acids are coded for amino acids are coded for in our strand?in our strand?

3 of course!3 of course!• Using your CODON Using your CODON

SHEET, translate the SHEET, translate the mRNA codons into 3 mRNA codons into 3 amino acidsamino acids

A

U

G

A

A

U

C

U

A

Translation ExampleTranslation Example

A

U

G

A

A

U

C

U

A

Ribosome tRNA brings

Ribosome

Ribosome

tRNA brings

tRNA brings

MethionineMethionine

AsparagineAsparagine

LeucineLeucine

Peptide Peptide BondBond

mRNA mRNA StrandStrand

Let’s do the whole thing Let’s do the whole thing together!together!

• DNA strand:DNA strand:

TACAAACATGGCTGATCGATTTACAAACATGGCTGATCGATT

• mRNA strandmRNA strand

AUG|UUU|GUA|CCG|ACU|AGC|UAAAUG|UUU|GUA|CCG|ACU|AGC|UAA

• Amino AcidsAmino Acids

MET-PHE-VAL-PRO-THR-SER-STOPMET-PHE-VAL-PRO-THR-SER-STOP

Protein Synthesis OverviewProtein Synthesis Overview