2. Transmission of Information
SUMMARY
DNA
REPLICATION
mRNA
TRANSCRIPTION
protein !
TRANSLATION
amino acids

4. Transcription Copies the DNA code to mRNA DNA unwinds
Only 1 strand is transcribed
Complimentary base pairing of nucleotides
C-G G-C T-A A-U
This pairing forms the mRNA
RNA polymerase helps form the new mRNA
initiation signal - “start here”
termination sequence - “stop synthesis”

5. Transcription
Termination
sequence
mRNA 5’
mRNA 3’

6. Translation Translation occurs on the ribosomes
Ribosome spheres dissociate into 2 parts
Each “half” of ribosome is made of...
rRNA
polypetides (enzymes)
60S unit (larger piece of ribosome)
40S unit (smaller piece of ribosome)

7. Translation Translation occurs on the ribosomes
mRNA is “stretched out” on ribosome
Nucleotides on the mRNA are grouped into 3s to form: “CODONS”
each CODON carries a 3 letter code to translate into an amino acid
“Anticodons” on tRNA will match-up with the codons

8. Ribosome rRNA rRNA 60 S codons 3’ 5’ 40 S mRNA
AUG
GCU
UUG
mRNA 5’ 3’
rRNA
40 S
AUG – School Starts in August

9. Genetic Code The Genetic Code
Broken in 1961 by Marshall Nirenberg and coworkers
Made poly-U mRNA and “fed” it to ribosomes
The only peptide made was phenylalanine
Therefore, UUU codes for Phe
Each AA is coded for by a sequence of 3 nucleotides on mRNA = CODON

11. Translation 4 STAGES in Protein Synthesis: Activation Initiation
Elongation
Termination

12. Activation Each AA is activated by reacting with an ATP
The activated AA is then attached to particular tRNA... (with the correct anticodon)
activated AA C G A
fMET
anticodon

15. Elongation
The new peptide is added on and the whole ribosome “translocates” or moves down one codon.
A new “A site” is available for another AA to add.

18. Termination
After the last translocation (the last codon is a STOP), no more AA are added.
“Releasing factors” cleave the last AA from the tRNA
The polypeptide is complete