1. If the DNA sequence is: 5’-ATGGCCA-3’ 3’-TACCGGT-5’ what is the mRNA sequence?

2. If the DNA sequence is: 5’-ATGGCCA-3’ 3’-TACCGGT-5’ what is the mRNA sequence?
mRNA: 5’-AUGGCCA-3’

3. Once mRNA is transcribed from DNA…
mRNA leaves the nucleus through nuclear pores
Ribosome is waiting in the cytoplasm
It binds to mRNA
Ribosomes do what in the cell?

4. Reading the mRNA
The ribosome uses the mRNA sequences to build a protein
It reads mRNA three bases at a time (or 3 letters at a time!)
These three letters are called a codon
Each codon codes for a specific amino acid.

5. Translation
Ribosome “reads” the first codon (3 nitrogen bases) on the mRNA.
The mRNA “chart” is consulted and the correct amino acid is requested.

6. Notice this chart has been built using mRNA codons NOT DNA triplets!
Notice that the chart has redundancy: more than one codon for the same amino acid
AUG = “start” building a new protein. UAA, UAG, UGA mean “stop’ building the protein. All mRNA’s start with AUG, so all DNA genes start with______?
mRNA codon chart

9. Checkpoint
Use the codon chart to determine what the amino acid would be for each codon
AUG
GUU
AAU
UUC
Why do we not see any T’s in this table?

10. Amino Acid to Protein Amino acids make up protein
Chains of amino acids are held together by peptide bonds
Once these are chained together, a protein is formed

11. tRNA Where?- Cytoplasm What?- Amino Acids
Why?- They carry amino acids back to ribosome to form the protein
tRNA’s hang out in the cytoplasm. Think of them as trucks that transport amino acids from where they float around in the cytoplasm, to the ribosome. The anticodon on the tRNA is complementary to the mRNA codon.

12. If the mRNA sequence is UAG what would the tRNA sequence be?

14. Ribosome slides along mRNA to next codon
Translation continues until the ribosome finds a STOP codon
Amino acids brought by the ribosome are joined with peptide bonds

15. Create this table in your notes and fill in the blanks. Remember:
-mRNA codon is complementary to the DNA triplet .
-the mRNA codon is used with the chart to determine the requested amino acid.
-the tRNA anticodon is complementary to the mRNA codon.
Dna active strand triplet
mRNA codon
tRNA anticodon
Amino acid requested
ATT
UAA
tryptophan
UUG

17. Exit Ticket
Using the details of transcription and translation, discuss how a DNA mutation will eventually led to an error in the protein.