2. Central Dogma of Genetics
Protein Synthesis
The process of reading the instructions in the DNA to make a protein.
Central Dogma of Genetics
DNA = instructions and is in the nucleus and can’t leave
But proteins are made in ribosomes
So protein synthesis takes 2 steps:
transcription
translation
DNA
RNA
protein

3. DNA
TRANSCRIPTION
RNA
TRANSLATION
Protein

4. Three Essential Types of RNA
mRNA (messenger): copies instructions in DNA and carries these to the ribosomes in the cytoplasm
tRNA (transfer): carries amino acids to the ribosome and mRNA
rRNA (ribosomal): composes the ribosome

5. TRANSCRIPTION Purpose: Carry the code/instructions out of the nucleus
(Remember: DNA never leaves the nucleus, and proteins are made in the cytoplasm by ribosomes.)
Location: Nucleus
Starts with: DNA
Ends with: mRNA

6. Transciption

7. TRANSCRIPTION Process: Unzip the gene that needs to be copied
Use complementary base-pairing rules to match RNA nucleotides with the exposed DNA nucleotides (Remember: RNA has uracil instead of thymine, so A binds with U)

8. Release the completed mRNA molecule (mRNA = messenger RNA)
DNA zips back up and the mRNA leave
the nucleus and enters the cytoplasm

9. Transcription: DNA is copied into a complementary strand of mRNA

10. Transcription – Try it! TAC GCT AGT ACG ATT AUG CGA UCA UGC UAA
DNA sequence (template):
TAC GCT AGT ACG ATT
mRNA sequence:
AUG CGA UCA UGC UAA

11. Translation Vocabulary
Genetic Code: code of instructions for how to make proteins
Codon: a set of 3 nucleotides on the mRNA
mRNA
(messenger)
Amino acid –monomer (building block) for making proteins, held together by peptide bonds
Anticodon: “complementary” 3 nucleotides on tRNA
tRNA
(transfer)

12. AMINO ACIDS  POLYPEPTIDE  PROTEIN

13. TRANSLATION
Purpose: Read/follow the instructions carried on the mRNA to make a protein Location: In the Cytoplasm at the Ribosome Starts with: mRNA Ends with: Protein

15. TRANSLATION Process: mRNA attaches to a ribosome.
Ribosome reads the mRNA codons (3 RNA nucleotides – like a triplet.)

16. tRNA (transfer RNA) molecules act like taxis to pick up and drop off the amino acids that match with the current codon.
tRNA’s continue to drop off amino acids, and the ribosome binds the amino acids together with peptide bonds.
When the “stop codon” is reached, the ribosome releases the completed protein.

17. Translation: interpreting the RNA message into a protein.

18. EACH tRNA carries only one kind of amino acid ANTICODON on tRNA
matches up with
CODON
on mRNA

19. The Genetic Code
The “words” of the DNA “language” are triplets of bases called codons
The codons in a gene specify the amino acid sequence of a polypeptide
there are 64 different codons but only 20 amino acids (some amino acids have more than one codon)
AUG is the “start codon”
UGA, UAA, UAG are all “stop codons”

20. The Genetic Code

21. Transcription and Translation: Try it!
DNA sequence (template):
TACGCTAGTACGATT
mRNA sequence:
AUGCGAUCAUGCUAA
Codons:
AUG CGA UCA UGC UAA
Amino Acids:
Met – Arg – Ser – Cys – stop
Resources I love:
Translation Animation:
Protein Synthesis Interactive:
Translation Animation: