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

7. 2. RNA contains uracil (U)
DNA has thymine (T)

9. 3.RNA molecule is single-stranded DNA is double-stranded

11. The Genetic Code
There are 20 amino acids found in proteins but only four different bases in messenger
RNA.
To code for all 20 amino acids, a sequence of three nucleotides must be used for
each amino acid.
Each triplet of nucleotides is called a codon.
The use of three nucleotides results in 64 different possible combinations (4364), which easily
code for the 20 amino acids that exist.

12. The Genetic Code

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

14. 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.

15. Promoter
Consists of a base-pair pattern, one that is high in adenine and thymine bases.
Adenine and thymine share only two hydrogen
It takes less energy to break two bonds; therefore, the RNA polymerase expends less energy opening up the DNA helix if it possesses a high concentration of adenine and thymine base pairs.

16. Question:
What is the enzyme responsible for the production of the RNA molecule?

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

18. DID YOU KNOW ?
There are three forms of the RNA polymerase in eukaryotes:
RNA polymerase I transcribes ribosomal RNA.
RNA polymerase II transcribes mRNA.
RNA polymerase III transcribes tRNA and other short genes that are about 100 base pairs in length.

19. 1. Transcription

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

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

24. 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

25. 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 mature RNA molecule that leaves the nucleus to the cytoplasm.

26. 5 cap
This 5 cap consists of 7-methyl guanosine, which forms a modified guanine nucleoside triphosphate
The cap protects the mRNA from digestion by nucleases and phosphatases as it exits the nucleus and enters the cytoplasm
It also plays a role in the initiation of translation.

27. poly-A tail.
200 adenine ribonucleotides is added to the 3 end by the enzyme poly-A polymerase.
The 3 end is known to contain a poly-A tail.
This whole process is known as capping and tailing.

28. 2. RNA Processing pre-RNA molecule intron exon exon exon
splicesome
exon
Mature RNA molecule
A-A-A
Poly A Tail

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

30. 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.

31. 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

33. 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.

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

35. 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.

36. 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

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

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

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

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

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

42. 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

43. 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

44. 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

45. 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

46. 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

47. peptide bonds U G A aa5 aa1 aa2 aa4 aa3 G A A G C U G C U A C U U C G
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 A C U
mRNA

48. Ribosomes move over one codon
peptide bonds U 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 A C U
mRNA
Ribosomes move over one codon

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

50. 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

51. Polyribosome
Groups of ribosomes reading same mRNA simultaneously producing many proteins (polypeptides).
incoming
large
subunit
small subunit
polypeptide
mRNA 1 2 3 4 5 6 7

52. 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?

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