1. Protein Synthesis
3.A.1.c.
Genetic information flows from a sequence of nucleotides in a gene sequence of amino acids in a protein.

2. The “Central Dogma” of Molecular Biology

3. Protein Synthesis
The process by which information stored in DNA (specific sequence of nucleotides) is used to produce proteins.

4. Remember how… RNA can boogie?
mRNA:  carries information from DNA to the ribosome
tRNA:  Molecules that bring specific amino acids to the ribosome, as dictated by the mRNA sequence.
rRNA:  Structural components of ribosomes
Regulatory RNA (RNAi): Control gene expression.

5. Transcription: DNA  RNA
Where?
-Within the nucleus (eukaryotes)
-Starts at promoter
-Ends at termination signal
Who?
-DNA
-RNA polymerase
-RNA
What?
- DNA is “rewritten” into mRNA

6. Transcription: DNA  mRNA
How?
RNA polymerase and transcription factors binds to promoter
DNA unwinds 1
RNA polymerase reads DNA 3’  5’ adds complementary nucleotides to form an mRNA strand 2
RNA polymerase reaches termination signal
mRNA and DNA are released 3

7. Transcription has just finished. What are we left with?
mrna OR
PRE-MRNA

8. Pre-mRNA Processing Addition of a poly-A tail to 3’ end
Help mature mRNA out of nucleus
Protect mRNA from degradation
Help ribosomes attach to mRNA in cytoplasm
Addition of a GTP (guanine triphosphate) or 5’ cap

9. Pre-mRNA Processing Splicing- removing introns
snRNPs recognize sequences at the ends of introns
Splicosomes remove introns and join exons

10. What is mRNA’s message? The message is sent in a code.
The code is written in the sequence of nitrogenous bases.

11. The Genetic Code 3 Nucleotides = 1 Codon
1 Codon = 1 Amino Acid OR a Signal
Amino Acids + Peptide bonds = Polypeptides
Polypeptide(s) + Folding, Twisting, and more = Protein
Signal Codons
AUG – Signal to START translation, Amino Acid Methionine
UAA
UAG Signals to STOP translation
UGA No Amino Acid Coding
Do an example on the board. Write…
AGU AUG CCU AUU GAG UAC CCC UAA GGA
Indicate the codons
How many codons will be transcribed?
What AAs are coded for?
Note: many amino acids have more than one codon.

12. Give it a whirl… AUGGACACACAUUAAUG AUG GAC ACA CAU UUA AUG Start Asp
Thr
His
Stop

13. Translation: RNA  Protein
Who?
-mRNA & Codons
-Ribosomes
-tRNAs
-Amino Acids
What?
- Amino acids are joined to form a polypeptide
Where?
-Within the cytoplasm
-Starts at AUG (start codon)
-Ends at a stop signal
How? 1
Initiation 2
Elongation 3
Termination

14. This is tRNA. It carries 1 amino acid. It has an anticodon.
They are related.
How, you ask?

15. Anticodons Methionine Anticodon Codon Imagine an mRNA molecule…
It has a codon: AUG
What it the compliment to AUG?
What amino acid does AUG code for?
Imagine a tRNA carrying methionine…
It has an anticodon: UAC
What is the compliment to UAC?
Anticodon
Codon

16. It has 2 subunits It is made of rRNA and proteins
This is a ribosome

17. Get it?
This is translation. JK

18. Step 1 Initiation: Get it together
Translation
Step 1 Initiation: Get it together
mRNA and rRNA (in the ribosome) interact, allowing the ribosomal subunit to bind to mRNA
(initiation) tRNA (carrying methionine) binds to mRNA at AUG (start) codon
Large ribosomal subunit comes to party too.
Who? Ribosome, tRNA
What? Bind to mRNA
Where? AUG codon
Why? They love each other : ) Anticodon?
If AUG starts all translation… is the first AA in every polypeptide methionine? Pretty much, but it can be removed later.

19. Elongation: Build it up
Translation
Elongation: Build it up
Second tRNA (with its own amino acid) attaches to the second codon
First tRNA releases its methionine
A peptide bond forms between the two amino acids
First tRNA leaves the ribosome
Ribosome moves down mRNA one codon
What is the red amino acid? Cytosine
What is the anticodon? ACA

20. Elongation: Build it up, more Translation New tRNAs keep moving in
Each new amino acid attaches with peptide bonds
Used tRNAs leave
Ribosomes keep moving down until…
What is the red amino acid? Cytosine
What is the anticodon? ACA

21. Translation Ribosomes keep moving down until…
What is the stop sign? UGA, UAA, UAG

22. NO amino acids are added at the stop codon
Translation
Termination: STOP
Ribosome reaches STOP codon
Polypeptide is released
NO amino acids are added at the stop codon
What is the red amino acid? Cytosine
What is the anticodon? ACA

23. Disassembly: It all comes apart
Translation
Disassembly: It all comes apart
All of the components come apart
Ribosomes move away to translate again or find a new mRNA
What is the red amino acid? Cytosine
What is the anticodon? ACA

25. Many ribosomes can translate one mRNA molecule at once!

26. In prokaryotes, translation and transcription are coupled
In prokaryotes, translation and transcription are coupled. They can happen at the same time! Why?

27. Fate of Polypeptides
Polypeptides fold and coil due to amino acid sequence (R-group interactions)
Post-translational modifications- addition of sugars, lipids, phosphate groups

28. Destinations

29. Fate of Polypeptides
Polypeptides fold and coil due to amino acid sequence (R-group interactions)
Post-translational modifications- addition of sugars, lipids, phosphate groups
Signal peptides (sequences of amino acids) target polypeptides for different locations (EMS, mitochondria, chloroplasts, nucleus, etc)

30. Mutations Changes to the genetic information in a cell (genotype)
can affect the phenotype of organisms by affecting protein structure and gene expression
Source of all new genes
Responsible for diversity of life

31. Mutations- Causes
Mutagens- substances that cause mutations by interacting with DNA
DNA Replication mistakes- 1/1,000,000,000 bases replicated in humans

32. Mutations
Can be positive, negative, or neutral, depending on where they occur

37. Chromosomal Mutations
Large scale mutations caused by changes to chromosome structure
Mistakes made during cell division can cause chromosome number abnormalities

38. Mutations and Fitness
Mutations only generate variation. Fitness is determined by the requirements of the environment.