1. Part 5 Translation 24-1

2. 24-2 Translation: mRNA and the Genetic Code Triplet code- codon 3 sequential Nitrogen bases in mRNA 64 different mRNA codons 61 code for different amino acids Redundant code (some AA have different codons) Protection against mutations Stop codons signal polypeptide termination Start codon  methionine (starts translation)

3. 24-3 Messenger RNA codons

4. 24-4

5. 24-5 Transfer RNA Transfer RNA (tRNA) tRNA transports amino acids to ribosomes Amino acid binds to one end, the opposite end has an anticodon Order of mRNA codons determines the order in which tRNA brings in amino acids

6. 24-6 Ribosomes & rRNA Ribosome Made in nucleolus  2 “subunits” Small subunit  1 rRNA + proteins Large subunit  2 rRNA + proteins + enzymes Binding site for mRNA and for 2 tRNAs Polyribosome  Several ribosomes may move along the same mRNA Multiple copies of polypeptide made at same time

7. 24-7 Translation Initiation, Elongation, Termination Initiation Small subunit attaches to mRNA at start codon Anticodon binds to start codon Large ribosomal subunit joins to the small subunit Elongation Amino acids added one at a time tRNA breaks away, and the ribosome moves forward one codon Movement of the ribosome is called translocation Termination Occurs at a stop codon Polypeptide is cleaved by an enzyme from the last tRNA Ribosome dissociates into 2 subunits

8. 24-8 Protein synthesis Fig. 24.12

9. 24-9 Gene expression Fig. 24.13