1. PROTEIN SYNTHESIS

2. Protein Synthesis The production (synthesis) of proteins. 3 phases:
1. Transcription
2. RNA processing
3. Translation
Remember: DNA  RNA  Protein

3. DNA  RNA  Protein Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell

4. DNA  RNA  Protein Prokaryotic Cell DNA mRNA Ribosome Protein
Transcription
Translation
DNA
mRNA
Ribosome
Protein
Prokaryotic Cell

5. Question:
How does RNA (ribonucleic acid) differ from DNA (deoxyribonucleic acid)?

6. RNA differs from DNA 1. RNA has a sugar ribose
DNA has a sugar deoxyribose
2. RNA contains uracil (U)
DNA has thymine (T)
3. RNA molecule is single-stranded
DNA is double-stranded

7. 1. Transcription Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell

8. 1. Transcription
The transfer of information in the nucleus from a DNA molecule to an RNA molecule.
Only 1 DNA strand serves as the template
Starts at promoter DNA (TATA box)
Ends at terminator DNA (stop)
When complete, pre-RNA molecule is released.

9. Question:
What enzymes are responsible for the production of the RNA molecule?

10. Answer: Helicase and RNA Polymerase
Helicase separates the DNA molecule by breaking the H-bonds between the bases.
RNA Polymerase moves along one of the DNA strands and links RNA nucleotides together.

11. 1. Transcription
DNA
pre-mRNA
RNA Polymerase

12. Question: DNA 5’-GCGTATG-3’
What would be the complementary RNA strand for the following DNA sequence?
DNA 5’-GCGTATG-3’

13. Answer:
DNA 5’-GCGTATG-3’
RNA 3’-CGCAUAC-5’

14. 2. RNA Processing Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell

15. 2. RNA Processing Maturation of pre-RNA molecules.
Also occurs in the nucleus.
Introns spliced out by splicesome-enzyme and exons come together.
End product is a messenger RNA molecule (mRNA) that leaves the nucleus to the cytoplasm.

16. 2. RNA Processing pre-RNA molecule intron exon exon exon
splicesome
exon
Messenger RNA molecule

17. Types of RNA Three types of RNA: A. messenger RNA (mRNA)
B. transfer RNA (tRNA)
C. ribosomal RNA (rRNA)
Remember: all produced in the nucleus!

18. A. Messenger RNA (mRNA)
Carries the information for a specific protein.
Made up of 500 to 1000 nucleotides long.
Made up of codons (sequence of three bases: AUG - methionine).
Each codon, is specific for an amino acid.

19. A. Messenger RNA (mRNA) Primary structure of a protein A U G C aa1 aa2
start
codon
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
codon 1
methionine
glycine
serine
isoleucine
alanine
stop
codon
protein
Primary structure of a protein
aa1
aa2
aa3
aa4
aa5
aa6
peptide bonds

20. B. Transfer RNA (tRNA) Made up of 75 to 80 nucleotides long.
Picks up the appropriate amino acid floating in the cytoplasm (amino acid activating enzyme)
Transports amino acids to the mRNA.
Have anticodons that are complementary to mRNA codons.
Recognizes the appropriate codons on the mRNA and bonds to them with H-bonds.

21. B. Transfer RNA (tRNA) methionine amino acid attachment siteU A C
anticodon
methionine
amino acid

22. C. Ribosomal RNA (rRNA)
Made up of rRNA is 100 to 3000 nucleotides long.
Important structural component of a ribosome.
Associates with proteins to form ribosomes.

23. Ribosomes Large and small subunits.
Composed of rRNA (40%) and proteins (60%).
Both units come together and help bind the mRNA and tRNA.
Two sites for tRNA
a. P site (first and last tRNA will attach)
b. A site

24. Ribosomes
Large
subunit P
Site A
Site
mRNA A U G C
Small subunit

25. 3. Translation Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell

26. 3. Translation Synthesis of proteins in the cytoplasm
Involves the following:
1. mRNA (codons)
2. tRNA (anticodons)
3. rRNA
4. ribosomes
5. amino acids

27. 3. Translation Three parts: 1. initiation: start codon (AUG)
2. elongation:
3. termination: stop codon (UAG)
Let’s make a PROTEIN!!!!.

28. mRNA Codon Translation Table

29. 3. Translation
Large
subunit P
Site A
Site
mRNA A U G C
Small subunit

30. Initiation G aa2 A U U A C aa1 A U G C U A C U U C G A codon 2-tRNA
anticodon A U G C U A C U U C G A
hydrogen
bonds
codon
mRNA

31. Elongation peptide bond G A aa3 aa1 aa2 U A C G A U A U G C U A C U U
3-tRNA G A
aa3
aa1
aa2
1-tRNA
2-tRNA
anticodon U A C G A U A U G C U A C U U C G A
hydrogen
bonds
codon
mRNA

32. Ribosomes move over one codon
aa1
peptide bond
3-tRNA G A
aa3
aa2
1-tRNA U A C
(leaves)
2-tRNA G A U A U G C U A C U U C G A
mRNA
Ribosomes move over one codon

33. peptide bonds G C U aa4 aa1 aa2 aa3 G A U G A A A U G C U A C U U C G
4-tRNA G C U
aa4
aa1
aa2
aa3
2-tRNA
3-tRNA G A U G A A A U G C U A C U U C G A A C U
mRNA

34. Ribosomes move over one codon
peptide bonds
4-tRNA G C U
aa4
aa1
aa2
aa3
2-tRNA G A U
(leaves)
3-tRNA G A A A U G C U A C U U C G A A C U
mRNA
Ribosomes move over one codon

35. peptide bonds G A aa5 aa1 aa2 aa4 aa3 G A A G C U G C U A C U U C G A
5-tRNA
aa5
aa1
aa2
aa4
aa3
3-tRNA
4-tRNA G A A G C U G C U A C U U C G A C C U
mRNA

36. Ribosomes move over one codon
peptide bonds G A
5-tRNA
aa5
aa1
aa2
aa3
aa4
3-tRNA G A A
4-tRNA G C U G C U A C U U C G A C C U
mRNA
Ribosomes move over one codon

37. Termination aa5 aa4 aa3 primary structure of a protein aa2 aa1 C C U C
terminator
or stop
codon
200-tRNA C C U C A U G U U U A G
mRNA

38. End Product
The end products of protein synthesis is a primary structure of a protein.
A sequence of amino acid bonded together by peptide bonds.
aa1
aa2
aa3
aa4
aa5
aa200
aa199

39. Question:
The anticodon UAC belongs to a tRNA that recognizes and binds to a particular amino acid.
What would be the DNA base code for this amino acid?

40. Answer:
tRNA - UAC (anticodon)
mRNA - AUG (codon)
DNA - TAC

41. When things go wrong…
Mutations: changes in the DNA sequence, that may be passed along to future generations.
Point mutations: a single base substitution
THE CAT SAW THE RAT
THE CAT SAW THE HAT
Deletion: a small DNA segment is lost
THE ATS AWT HER AT
Insertion: a segment of DNA is added
THE CAT SAW THE BHAT

42. Mutations
Frame-shift mutation: modification of the reading frame after a deletion or insertion, resulting in all codons downstreams being different.
For example:
THE RAT SAW THE CAT AND RAN
If you take out the “R” in “RAT” and shift the frames, you get:
THE ATS AWT HEC ATA NDR AN
The resulting sentence (or mRNA message) is meaningless!

43. Mutations
Somatic mutations: occur in body cells, or cells that do not lead to gametes.
Somatic mutations that occur in leaves, roots or stems are usually not passed on to future generations… UNLESS the plant is reproduced asexually.