1. Quiz tiiiiime What 3 things make up a nucleotide?
What molecule is used as a “battery” to allow the connection of nucleotides to happen?
What enzyme is in charge of unzipping and unwinding DNA in replication?
Why are telomeres important
What does the “m” in mRNA stand for?
What is a codon?
What is the name of the box that acts as a promoter for transcription?
What is transcription?
What type of molecule are DNA Polymerase, RNA polymerase, and topoisomerase? How do you know?

2. Protein Synthesis

3. General Information Also called gene expression
DNA provides the blueprints for the building of proteins

4. General Information Involves two processes:
Transcription- copying DNA into mRNA
Translation- translates the code from nucleic acid into amino acid at the ribosome

5. Evolutionary Advantage of Transcription and Translation
DNA is protected inside the nucleus
Using an RNA intermediate allows multiple copies of a protein to be made at once because many mRNA molecules can be made from one gene, then translated repeatedly

6. Prokaryotes vs. Eukaryotes
Only one compartment (no nucleus)
Transcription and Translation occur simultaneously

7. Prokaryotes vs. Eukaryotes
Transcription occurs in the nucleus
The primary transcript is then modified (RNA processing) before leaving the nucleus
Translation occurs in the cytoplasm at the ribosome

8. The Genetic Code
Triplet Code- the flow if information from gene (DNA) to protein is written in the DNA as non-overlapping, three-nucleotide segments
Template Strand:
The mRNA is complimentary to the template strand
The DNA is read in the 3’ to 5’
The mRNA is synthesized and read from 5’ to 3’

9. The Genetic Code Codons- each three base sequence on the mRNA strand
Each codon codes for a specific amino acid

10. Redundant but not Ambiguous
Redundant- multiple codons can code for the same amino acid
Not Ambiguous- no codon codes for more than one amino acid

11. Special Codons
AUG= start
UAA, UAG, UGA= stop

12. Transcription

13. Initiation RNA polymerase binds to the promoter
The promoter is a specific sequence that tells the RNA polymerase where to bind and determines what DNA strand will serve as the template
In eukaryotes, specific proteins called transcription factors assist the RNA polymerase in binding and forming the transcription initiation complex

14. Initiation

15. Elongation
RNA polymerase adds nucleotides to the 3’ end of the growing RNA molecule
Complimentary base pairing occurs
The new RNA molecule peals away from the DNA template and the DNA reforms

16. Termination
In prokaryotes, the RNA polymerase detaches after the termination signal is transcribed
In eukaryotes, the RNA polymerase transcribes the polyadenylation signal sequence then the mRNA is cut off of the RNA polymerase

17. RNA Processing
EUKARYOTIC CELLS ONLY

18. Using pages 334 and 335… Describe RNA processing…
What is it?
What are two examples?
What is the purpose of RNA processing?
Describe Introns and Exons using Figure 17.10

19. Altering of the Ends of the mRNA
5’ cap- modified guanine molecule added on the 5’ end
Poly-A-tail adenine nucleotides are added to the 3’ end
Functions:
Facilitate export from the nucleus
Protect the mRNA from degradation by enzymes
Assist the ribosomes in attaching in the cytoplasm

20. RNA Processing

21. RNA Splicing Removal of large portions of the mRNA
snRNPs (“snurps”) recognize and cut out areas of the mRNA
Introns- the portions of the mRNA that are removed
Exons- the portions of the mRNA that exit the nucleus

22. Translation- Important Components

23. Transfer RNA, tRNA Translates nucleotides into amino acids
One end has an anticodon, complementary to the mRNA codon
The other end is bound to an amino acid
Excellent example of how structure fits function

24. Ribosomes Contain three sites for holding tRNA:
P site- holds the growing polypeptide chaing
A site- holds the tRNA that is carrying the next amino acid in the chain
E site- where the tRNA leaves the ribosome
Exit Tunnel= where the polypeptide leaves the ribosome

25. Translation- The Process

26. Initiation
Small ribosomal subunit binds the mRNA and the initiator tRNA
Subunit scans the mRNA until it reaches the start codon, establishing the correct reading frame as the tRNA hydrogen bonds to the start codon

27. Initiation
Translation initiation complex forms- the large ribosomal subunit attaches with the assistance of initiation factors and an expenditure of energy

28. Elongation

29. Elongation The ribosome reads the mRNA in the 5’ to 3’ direction
Anticodon of the incoming tRNA hydrogen bonds to the mRNA codon in the A site
The peptide bond forms between the amino acid on the tRNA of the A site and the growing polypeptide chain in the P site
Translocation of the tRNA shifts the A site tRNA to the P site and the P site tRNA to the E site so it can exit

30. Termination Release factor: The polypeptide is released
Added when stop codon is reached
Causes the addition of a water molecule to the end of the polypeptide
The polypeptide is released

31. Forming a Functional Protein

32. Protein Folding Folding occurs as the protein is being synthesized
Folding is dependent on
The properties of the peptide chain
The physical and chemical properties of the environment
WHY MIGHT THIS BE A PROBLEM???

33. Chaperonins
Proteins that assist in the proper folding of other proteins by shielding them form the cell environment

34. Post-Translational Modification
Chemical modification by the attachment of sugars, lipids, phosphate groups, or other components
Enzymes may remove one or more amino acids from the N-terminus
Single polypeptides may by cut into two or more smaller pieces

35. Denaturation
The changes in a protein’s native conformation that renders it biologically inactive
Factors that cause denaturation:
Change in the environment
Change in temperature
Change in pH

36. Changes in Environment
If moved from an aqueous environment to a nonpolar organic solvent, the protein will turn inside out
Chemicals can disrupt disulfide and hydrogen bonds that stabilize secondary and tertiary structure

37. Changes in Temperature
Excessive heat can cause movement to overpower sensitive hydrogen bonds
Excessive cold will slow the protein down substantially

38. Changes in pH All proteins have an optimal pH at which they function
Optimal pH is not necessarily 7