1

Protein SynthesisProtein SynthesisTranscription and Transcription and

TranslationTranslation

DNA’s destiny!DNA’s destiny!http://www.brainpop.com/science/cellularlifeandgenetics/dna/

2

What does DNA really do?What does DNA really do?A. The DNA code must code for something A. The DNA code must code for something

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

B. The DNA alphabet essentially codes for B. The DNA alphabet essentially codes for amino acidsamino acids

C.C. Which are the Which are the building blocksbuilding blocks for……. for…….1.1. PROTEINSPROTEINS!!!!!!!!!! !!!!!!!!!!

3

What is RNA?What is RNA?

4

Where is RNA Found? Where is RNA Found?

__________________________________

__________________________________

__________________________________

RNA Type Found Function

Messenger (mRNA) Nucleus/Cytoplasm Decodes DNA

Transfer (tRNA) At the ribosomeDecodes mRNA into amino acid codes

Ribosome (rRNA) ribosomeHelps connect amino acids to make protein

5

From DNA to Protein: From DNA to Protein:

D. This occurs in several organized steps in D. This occurs in several organized steps in 2 2 phasesphases

1. PHASE 1:1. PHASE 1:a.a. Transcription Transcription

1) DNA IS 1) DNA IS TRANSCRIBEDTRANSCRIBED INTO INTO READABLE READABLE FORM FORM ((mRNAmRNA))

2.PHASE 2:2.PHASE 2:a.a. Translation Translation

1) mRNA IS 1) mRNA IS TRANSLATEDTRANSLATED TO TO CODECODE FOR FOR AMINO AMINO ACIDSACIDS

6

Transcription: The Video ClipTranscription: The Video Clip

7

Phase 1: TranscriptionPhase 1: TranscriptionA. Occurs A. Occurs INSIDE THE NUCLEUSINSIDE THE NUCLEUSB. B. DNA DNA strands strands separateseparateC. C. Complimentary RNAComplimentary RNA bases bases take their take their

placesplaces along DNA with the help of along DNA with the help of enzymesenzymes1. RNA bases are 1. RNA bases are A, C, G, and UA, C, G, and U (uracil) (uracil)2. 2. UU instead of instead of TT!!D. This D. This creates creates an an mRNAmRNA strand strand

Let’s see this in action!

8

Let’s practice making a complimentary mRNA from a DNA strand! Remember: C-G and A-U

DNA mRNA

C

G

A

T

T

A

G

A

T

G

C

U

A

A

U

C

U

A

9

Protein Synthesis: The Video ClipProtein Synthesis: The Video Clip

10

Let’s talk about Proteins…the Let’s talk about Proteins…the ultimate resultultimate result

A. Long A. Long chainschains formed by formed by 20 20 different different amino acidsamino acids

B. Protein B. Protein shapeshape is is determineddetermined by by DNADNA sequence!sequence!

C. C. DNA DNA transcribed to transcribed to mRNAmRNAD. D. mRNAmRNA now now codescodes for for amino acidsamino acids!!

HOW YOU THINK??HOW YOU THINK??

12

Proteins…the ultimate result cont.:Proteins…the ultimate result cont.:So glad you asked!!!So glad you asked!!!

E. E. 3 3 mRNA mRNA basesbases code for an code for an amino acidamino acid!!

1. Ex. GCU codes for 1. Ex. GCU codes for AlanineAlanine

2. This is called a 2. This is called a CODONCODON

F. Each amino acid has F. Each amino acid has more more than one codon!than one codon!

G.G. Polypeptide:

1. String of amino acids

13

1. The strand we made earlier is:1. The strand we made earlier is:G C U | A A U | C U A

2. If 3 bases code for an amino acid, how 2. If 3 bases code for an amino acid, how many amino acids are coded in our many amino acids are coded in our strand?strand?

3 of course!3 of course!G C U | A A U | C U A

Alanine | Asparagine | Leucine

3.Coding and stringing amino acids together is called TRANSLATION!

H. Let’s look at the mRNA we transcribed H. Let’s look at the mRNA we transcribed earlier!earlier!

14

Phase 2: TranslationPhase 2: TranslationA. A. mRNAmRNA is is shippedshipped out of out of nucleus nucleus for for

translationtranslation

B. **Review** Which organelle is in B. **Review** Which organelle is in charge of protein synthesis?? (Hint: very charge of protein synthesis?? (Hint: very tiny little buggers)tiny little buggers)

RIBOSOMES!RIBOSOMES!

C. C. mRNAmRNA binds to a binds to a ribosomeribosome for for translationtranslation!!

15

Steps of TranslationSteps of Translation

1. mRNA binds to ribosome

2. Ribosome translates the codons on the mRNA

3. This signals a tRNA to bring the correct amino acid

4. tRNA drops off amino acid

16

Steps to Translation cont.:Steps to Translation cont.:5.5. Ribosome moves to next

codon6.6. Another tRNA comes with

next amino acid7.7. Amino acids are connected

by PEPTIDE BONDS (AA-AA-AA, etc)

8. This continues until all of 8. This continues until all of the mRNA has been the mRNA has been readread

9. End result: 9. End result: a a proteinprotein!!!!!!!!!!!!!!!!!!

17

Table is based on mRNA

18

Ex. Name the amino acids that make up the DNA strand: ATC GCT AAG CCT GGC

a) mRNA: transcribe (decode) the codons: (remember there aren’t any T’s) - A-U, C-G

b) tRNA: bring in the amino acids needed to make the protein molecule: list them in order

YOU TRY…..

19

DNA: ATC GCT AAG CCT GGC

mRNA: UAG CGA UUC GGA CCG

tRNA: AUC GCU AAG CCU GGC

AA: XXX - arg - phe - ala - gly

20

You have DNA in nucleusDNA in nucleus (START TRANSCRIPTION)

DNA is transcribed to mRNA U’s instead of T’s!

mRNA leaves nucleus (START TRANSLATION) mRNA

binds to ribosome Ribosome translates codons Translating signals tRNA to bring

amino acids Amino acids are bound together by

peptide bonds

OVERVIEW OF PROTEIN SYNTHESISOVERVIEW OF PROTEIN SYNTHESIS

21

Memory Device for Protein Synthesis

TTransfer RNA bringsransfer RNA brings AAmino acids tomino acids to RRibosomeibosome TTranslationranslation

TTranscriptionranscription UUnzip the DNAnzip the DNA MMakesakes MMessenger RNAessenger RNA