1. Protein Synthesis
Przeworski

2. Protein Synthesis
Instructions for proteins are stored as DNA in the nucleus (one gene = one protein)
The ribosomes that actually make the proteins are outside in the cytoplasm
DNA is too large to exit through nuclear pores… it requires a messenger to send the instructions

3. Nucleus
mRNA
Transcription
DNA
Translation
Cytoplasm
Ribosome
Protein

4. Transcription
In transcription, a copy of a protein recipe called messenger RNA (mRNA) is made from DNA
mRNA is half the width of DNA and can leave the nucleus

5. DNA vs RNA Deoxyribonucleic acid Contains the sugar deoxyribose
Double-stranded
Bases are G, C, A, T
Ribonucleic acid
Contains the sugar ribose
Single-stranded
Bases are G, C, A, U
U = Uracil, replaces Thymine
G still pairs with C
A pairs with U T D P
Thymine
Nucleotide
(DNA) U R P
Uracil
Nucleotide
(RNA)

6. A now pairs with U (instead of T)
The RNA bases are slightly different.
C still pairs with G
A now pairs with U (instead of T) C D P G R P G D P A D P U R P T D P C D P C R P G D P

7. Step One: Initiation
RNA polymerase locates the section of DNA (gene) that it wants to transcribe.
It attaches to the promoter region, causing DNA to unzip with the help of a Helicase.
Polymerase and Helicase are enzymes (special proteins!)

8. Step two: Elongation
Once DNA is unzipped, the Polymerase transcribes the DNA section
Free-floating RNA nucleotides attach
This is just like Replication, but with the base uracil instead of thymine. (A-U and C-G)

9. Step Two: Elongation
For example, if the DNA strand read ACGT, then the RNA would be UGCA.
This continues until the entire gene is transcribed, ending with the Stop sequence.

10. Step Three: Termination
Once the stop sequence is reached, the RNA strand detaches
It is then processed into mRNA by adding a 5’ cap and a poly-A tail (for protection)
Finally, the mRNA leaves the nucleus! (DNA rezips)

11. Nucleus
mRNA
Transcription
DNA
Translation
Cytoplasm
Ribosome
Protein

12. Transcription clip (real time)

13. Group Poster PRoject A legible title
In your groups of four (each table should work with the one behind them, and turn your chairs around)
You will be given a step of transcription or DNA vs RNA
For your assigned topic, make sure there is:
A legible title
Large writing describing what occurs in the step (or large writing that explains the differences between DNA and RNA)
A large picture, colored. (All writing should be in marker)

14. Translation - Overview
In translation, a ribosome uses an mRNA recipe to select and put together a sequence of amino acids
mRNA is read 3 bases at a time (3 bases = 1 codon)
Each codon = 1 amino acid
DNA template: A T A G A T C C A
mRNA: U A U C U A G G U
Amino Acid 1
Amino Acid 2
Amino Acid 3

15. DNA: A T A G A T C C A mRNA: U A U C U A G G U Tyrosine Leucine
Glycine

16. Special Codons
As a ribosome reads an mRNA transcript, special codons tell it where to start and stop making a protein
START codon: A U G (must memorize!)
mRNA: A A G G U C A U G C C A C G U U A A
Amino Acid: Methionine Proline Arginine STOP

17. Step onE
The mRNA from the nucleus makes its way through the cell to a free-floating ribosome and attaches to it.

18. Step two: Each set of three RNA bases is called a codon.
For this sequence: AUGCUA, AUG is a codon and CUA is another codon.
Each codon codes for a single amino acid, which is the building block of proteins.

19. Step two:
At the ribosome, the codon of mRNA pairs with its anti-codon (correct base pairs)
For our earlier codons, AUG would pair with UAC and the anticodon for CUA is GAU.

20. Step two:
tRNA (transfer RNA) translates each codon into one amino acid.
Amino Acids are linked with peptide bonds to form a chain

21. Step three:
Once the amino acids are linked with a PEPTIDE BOND, the mRNA strand moves like an assembly line, releasing the first codon and anticodon.

22. Step four
The chain of amino acids (polypeptide chain) will then form a protein.
There are 20 different amino acids, which are the codes for all living things!

23. Wheel of codons!! Input the mRNA codon, get out the amino acid!
Special amino acids:
AUG= start
UGA=stop

25. Types of RNA Structure Function mRNA Single strand
(messenger)
Single strand
Takes copied DNA recipe to ribosome
tRNA
(transfer)
Has anticodon on one end, carries amino acid on the other
Delivers amino acids to ribosomes
rRNA
(ribosomal)
Folded into ribosome shape
The ribosome itself is made of this

26. Given the mRNA codon GCU, what is the amino acid?
Alanine

27. Practice time! Given mRNA codon of AUG, what is the amino acid?
Methionine (Start!)