1. NOTES: Chapter 13 - RNA & Protein Synthesis
Vocabulary:
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
Transcription
RNA Polymerase
Codon
Translation
Anticodon
Key Concepts:
What are the 3 main types of RNA? What is transcription?
What is translation?

2. Genes and Proteins:
RECALL: the sequences of nucleotides in DNA contain INFORMATION!
This information is put to work through the production of PROTEINS.

3. What do proteins do for the body?
Proteins are diverse:
 control chemical messages in cell;
 direct the synthesis of carbo’s, lipids, and nucleotides;
 enzymes;
 give the cell structure and
movement
Goal of protein synthesis:
MAKE A PROTEIN

4. Protein Structure: RECALL: proteins are polymers of AMINO ACIDS
The sequence of nucleotides in each GENE contains the information for the sequence of AMINO ACIDS in a single protein
Each human cell contains
about +/- 35,000 genes

5. RNA Like DNA= made of nucleotides copy of DNA segment
3 main types: mRNA, rRNA, tRNA
3 differences
1) sugar = ribose
2) single stranded
3) instead of the base thymine (T), RNA uses URACIL (U)

7. Job of RNA: Function in Protein Synthesis

8. Role of RNA – an analogy
Imagine what goes into a new car being built on an automobile assembly line:
Engineers make the design and tell the workers how to make the cars;
Workers follow the directions to build the cars;
Suppliers bring parts to the assembly line so they can be installed in the car

9. Role of RNA – an analogy Now imagine what goes into PROTEIN SYNTHESIS:
DNA provides the “workers” with the instructions for making proteins;
The workers (RNA molecules!) follow the instructions from DNA and build the proteins;
Other workers (other RNA molecules) bring parts (AMINO ACIDS) over to the assembly line

10. 3 Types of RNA:
Messenger RNA (mRNA): brings information from the DNA in the nucleus out to the ribosomes;
Ribosomal RNA (rRNA): clamp on to the mRNA and use its information to assemble amino acids into a protein;
Transfer RNA (tRNA): the “supplier”; transports amino acids to the ribosome

11. DNA  RNA
How does the information in DNA , which is found in the nucleus, get out to the ribosomes in the cytoplasm…it needs a “MESSENGER”!

12. Transcription Transcribe: to make a copy
Step #1 (of 2) of protein synthesis
Transcribe: to make a copy
transcribing DNA information (gene instructions) into mRNA
mRNA can leave the nucleus  ribosomes in the cytoplasm
special base sequences in DNA are recognized by RNA as “start” and “stop” signals
“Start” sequence called PROMOTER region of DNA

13. Details of the Process
1. RNA polymerase attaches to DNA at the site where instructions for the needed protein begins & it separates the 2 DNA strands

14. 2. RNA polymerase synthesizes the mRNA strand using complementary base-pairing

15. Remember…there aren’t “T” bases in RNA
“C” binds with “G”
DNA “A” binds with RNA “U”

16. Which strand was copied? A or B

17. 3. when RNA polymerase reaches the end or "STOP" part of the genetic code for that protein, it releases
4. DNA re-zips
 5. finished mRNA (message) leaves the nucleus and goes to a ribosome in the cytoplasm

18. Bases are grouped by 3
Called a CODON (“code”)

19. Transcription
Translation

20. Transcription ends with mRNA which will exit the nucleus to the cytoplasm
So… if transcription is the first step of Protein Synthesis, what happens next in the cytoplasm?

21. TRANSLATION
Making a protein (string of amino acids): translating from the language of nucleic acids into a polypeptide
How does it go from mRNA (copy of DNA) to amino acids (building blocks of proteins)?
 A group of 3 mRNA bases makes up a “codon” (think of as a “code word”)
 each codon specifies a particular amino acid
 there are “start” and “stop” codons

22. The Mechanism... 1) mRNA attaches onto the ribosome
 3 nucleotides of mRNA = codon
2nd kind of RNA= ribosomal RNA (rRNA)
 makes up the majority of the ribosome

23. The Mechanism continued...
3rd kind of RNA= transfer RNA (tRNA)
 carries amino acids to the ribosomes (amino acids join together)
 3 nucleotides of tRNA that “match” or complement the mRNA = anticodon
 there are 64 different tRNA molecules (more than 1 for each amino acid)
 REDUNDANCY of the CODE!!

24. tRNA
Amino acid
tRNA anticodon
mRNA codon

25. amino acid
tRNA
anticodon
codon (mRNA)

26. The Mechanism continued...
2) By matching the codon of mRNA to the anticodon of tRNA, the correct amino acid is put into place
Next tRNA goes here!!!!

27. The Mechanism continued...
3) a peptide bond is formed between the 2 amino acids

28. The Mechanism continued...
4) protein chain continues to grow until a “stop” codon is reached on the mRNA
 no tRNA exists for “stop” codons

29. tRNA anticodon mRNA codon
Amino acid
·  Molecules of tRNA are specific for only 1 amino acid
-one end of tRNA attaches to a specific amino acid
-the other end attaches to mRNA codon by base pairing
(anticodon = a sequence of 3 bases on tRNA)
tRNA anticodon
mRNA codon

30. ● tRNA’s decode the genetic message codon by codon

32. This table shows
the “dictionary”
for the codons
and their
corresponding
amino acids

34. Transcription
Translation

37. Translation: All At Once

38. PROTEIN SYNTHESIS: All At Once

39. PROTEIN SYNTHESIS
DNA
Step 1. TRANSCIPTION
(nucleus)
mRNA
Step 2. TRANSLATION
(ribosome)
tRNA
PROTEIN

40. Protein Synthesis:
the whole
process

41. Protein Synthesis—video

42. PRACTICE:
DNA: T A C C G C G G T T T A A C T
RNA:
amino
acids:

43. PRACTICE: DNA: T A C C G C G G T T T A A C T
RNA: A U G G C G C C A A A U U G A
amino
acids:

44. PRACTICE: DNA: T A C C G C G G T T T A A C T
RNA: A U G G C G C C A A A U U G A
amino
acids: met – ala - pro asn STOP