1. RNA 2
Translation

2. Big Picture DNA Gene Protein Trait 4 bases Base paring Double helix
Observed physical Characteristics
Segment of specific location.
Instructions for making Proteins

3. So Far... DNA contains genes (segments of DNA at a specific location)
Genes have the instructions to make specific proteins
On the gene, an RNA copy of the DNA is made (Transcription)

4. Quick Review What does a protein do?
“Machinery” of the cell: pumps, enzymes, contraction, cytoskeleton...
Sure...but what are they?

5. Proteins are... ...polymers of amino acids A “string of beads”
Amino acids have
Central carbon atom
Amino group
Acid Group
“Side Group”
There are 20 amino acids used in proteins, all with different “side groups.”

6. Proteins

7. Protein Chains
The order and the properties of the amino acids of the 20 different types give proteins their unique characteristics and abilities.

8. how do we get from a gene to a protein?
It’s all about the code...
We need a code that can tell us which amino acids to put where to get the results we want.

9. Genetic Code
It takes 3 DNA nucleotides to “code for” the 20 possible amino acids
1 molecule would give us how many options?
4 different bases in one location: A or T...
4 options or 41 (not enough)
2 molecules would give us...?
AA or AT or AG or...
16 options or 42 (not enough)
3 molecules gives us...?
64 options or 43 (plenty)

10. Using the 64 combinations
One combination “starts” the sequence
DNA sequence: TAC
mRNA sequence: AUG
3 combinations “stop” the sequence
DNA sequences: ATT, ACT, ATC
mRNA sequences: UAA, UGA, UAG
Each 3-letter mRNA sequence is called a codon.

11. Codons More than one codon can code for an amino acid
Alanine = GCU, GCC, GCA, GCG
Each codon only codes for one amino acid.
GCU is always alanine
The redundancy, or back-up duplicates, in the code offer some protection from errors

13. Amino Acids Asparagine (Asn) Lysine (Lys) Glutamic Acid (Glu)
Phenylalanine (Phe)
Leucine (Leu)
Isoleucine (Ile)
Valine (Val)
Serine (Ser)
Proline (Pro)
Threonine (Thr)
Alanine (Ala)
Tryosine (Tyr)
Histidine (His)
Glutamine (Gln)
Asparagine (Asn)
Lysine (Lys)
Glutamic Acid (Glu)
Aspartic Acid (Asp)
Cystenine (Cys)
Tryptophan (Trp)
Argenine (Arg)
Glycine (Gly)
Methionine (Met)
Start codon

14. Codons Codons are like words The letters tell you what the word means
Which amino acid to use
The words for a sentence
The combination of amino acids that produces the working protein.

15. How can we tell what Amino Acid is used?

16. We read the Amino Acid Chart

18. How to we Read the Amino Acid (AA) Chart?
The chart is read by looking at the codon on the mRNA strand
Steps:
Read the mRNA codon and then look to chart to find the corresponding amino acid
Left,
Up,
Right
“Clockwise starting from the left”

19. Let’s Practice

20. DNA Strand:
TAC
mRNA Strand:
AUG
Amino Acid:
Met (Methionine)
DNA Strand:
TACGTAAAT
mRNA Strand:
AUGCAUUUA
Amino Acid:
[Met][Tyr][Leu]

21. How do we actually make proteins?
Translation

22. Steps of Making Proteins√
Transcription:
mRNA Copy
Translation:
Protein Synthesis
Proteins

23. Making Proteins We already have: Protein making instructions (mRNA)
Translation:
Protein Synthesis
We already have:
Protein making instructions (mRNA)
We still need:
A Workbench
Amino Acids

24. mRNA to Proteins
To start the process, the mRNA is transported to a ribosome (workbench)
In the ribosome, the mRNA will provide directions for how to make proteins
This process is called translation
Translation = the creation of proteins by linking chains of amino acids together (polymers)
Occurs in cytoplasm or attached to RER.

25. mRNA: messenger RNA
tRNA: transfer RNA
rRNA: ribosomal RNA
The Players

26. Types of RNA mRNA: messenger RNA tRNA: transfer RNA
rRNA: ribosomal RNA
Types of RNA

27. Types of RNA mRNA: messenger RNA tRNA: transfer RNA
rRNA: ribosomal RNA
Types of RNA

28. Types of RNA mRNA: messenger RNA tRNA: transfer RNA
rRNA: ribosomal RNA
Types of RNA

29. The Players mRNA: messenger RNA tRNA: transfer RNA Ribosomes:*
rRNA + Proteins

30. Transfer RNA: (tRNA)
It’s job is to transfer amino acids from cytoplasm to ribosome
Anticodon is located on the bottom (base pairs to mRNA codon)
Must match the mRNA codon exactly in order to pair
Amino acid attaches to the top
The specific amino acid that the tRNA carries is determined by its anticodon

31. Ribosome The ribosome has two major parts (called subunits)
The large and small subunits
Both are made from proteins and ribosomal RNA (rRNA)
mRNA is pulled through and read only when the subunits join together
Ribosome

32. Ribosome Reads the mRNA between the subunits Also has space for 3 tRNA
Called the P site, A site, E site

33. Disclaimer: You are not expected to know the exact details of Translation, but it sometimes is helpful to see how the process works to better understand it. I will tell you what you should and should not know.

34. Translation
Three parts
Initiation
Elongation
Termination

35. Initiation Ribosome locks around the mRNA
tRNA pairs with start codon AUG,
tRNA amino acid is Met (methionine)

36. Elongation
Codon Recognition, an incoming tRNA binds to the codon in right site
Bond formation, the ribosome forms a bond between the new amino acid and the growing protein chain

37. Elongation Continued
the tRNA in the right site is moved to the middle site, taking the mRNA along with it, middle site open to next tRNA
The tRNA in the right site moves to the left site and is released from the ribosome, the ribosome shifts the mRNA by one codon

38. Termination
When the ribosome reaches the termination codon (UAG,UAA,UGA) on the mRNA
The protein chain in released
Subunits separate

41. Practice Turn to your neighbor...
Describe the summary of translation in your own words
Switch and have the other neighbor try it
Be Prepared to share your summary with the class

42. Translation Summary mRNA is sent from nucleus to cytoplasm
Ribosome attaches to the mRNA in the cytoplasm
tRNA’s bring the amino acids to the ribosome
It is the anticodon of the tRNA that determines which AA the tRNA carries
The first tRNA brings the AA Met to the start codon

43. Translation Summary
The mRNA is read by the ribosome (pulled like a tape)
The mRNA codon is matched to the tRNA anticodon
If the codon & anticodon match, the AA is added to the protein chain
When the stop codon is reached on the mRNA, the ribosome separates and the protein is released

44. Put it all together Take out a half sheet of paper
Explain how a protein is made beginning from DNA
Be sure to include Transcription & Translation
This is a great level 3 question

45. Practice
Protein Synthesis
Snorks