Protein Synthesis

Codes!

• DNA contains codes– Codons

• 3 nucleotide bases = amino acid

– Sequence of amino acids = proteins

– DNA copied = mRNA (messenger RNA)

Transcription and Translation

• Transcription– Creation/synthesis of mRNA from a DNA

template strand

• Translation– Ribosomes make proteins using the mRNA

strand made by transcription

Transcription

• One strand of DNA is copied

• Creates mRNA– mRNA travels OUT of the nucleus to the

cytoplasm (where the ribosomes are)

mRNA

• Ribonucleic Acid

• Structurally similar to DNA– U instead of T– Single-stranded

• Used to create proteins

• AUGACGGUU

Vocab

• Codon– Basic unit of the genetic code– Sequence of 3 adjacent neucleotides in DNA

or mRNA

• Amino Acid– RNA codon

Translation3 Main Steps

1. Initiation

2. Elongation

3. Termination

Translation StepsInitiation

1. Ribosomes attach to an mRNA strand

Translation StepsElongation

2. Translation begins at the AUG codon

AUG means GO!

tRNA Molecules

tRNA

– Recognize both specific mRNA codons and the amino acids that match those codons

– Contains an “anti-codon” which attracts specific amino acids

• Similar to the complimentary base pairing rule

Translation StepsElongation

3. Transfer RNA (tRNA) molecules carry anti-codons

These anti-codons find complimentary codons and attach them to the ribosome and mRNA

Translation StepsElongation

4. The ribosome travels down the mRNA and reads the codons

Translation StepsElongation

5. The ribosome pauses at each codon and waits for the tRNA to bring the correct amino acid

6. Each amino acid is bound together by a Peptide Bond!

Translation StepsTermination

7. The process continues until the ribosome reaches a stop codon

Translation StepsTermination

8. Everything breaks apart!

Final peptide bonds are created, the ribosome breaks apart, and the polypeptide (protein) is released

Translation StepsTermination

9. The Protein (polypeptide) folds into its specific shape.

Shape determines function!

10.The Protein is ready tobe used by the body!

64 codons code for 20 different amino acids