1. KEY CONCEPT Translation converts a mRNA message into a polypeptide or protein.

2. Amino acids are coded by mRNA base sequences.
Translation converts mRNA messages into polypeptides.
A codon is a sequence of three nucleotides that codes for an amino acid.
codon for
methionine (Met)
leucine (Leu)

3. Reading Frame: series of 3 non-overlapping nucleotides read in order
Common Language: the genetic code is shared by all organisms
Start codon: signals the start of translation (AUG –Met)
Stop codon: signals the end of an amino acid chain
Anticodon: 3 nucleotides on a tRNA molecule that bind to a complementary mRNA molecule
Ribosome: site of protein synthesis; made of rRNA and protein; catalyses formation of peptide bonds between amino acids
tRNA: type of RNA that carries amino acids to the ribosome (think – taxi)

4. Label these structures
1. amino acid
2. peptide bond
3. large ribosomal subunit
4. tRNA
5. codons
6. small ribosomal subunit
7. mRNA
8. anticodon

5. The genetic code matches each codon to its amino acid or function.
The genetic code matches each RNA codon with its amino acid or function.
three stop codons
one start codon, codes for methionine

6. A change in the order in which codons are read changes the resulting protein.
Regardless of the organism, codons code for the same amino acid.

7. Amino acids are linked to become a protein.
An anticodon is a set of three nucleotides that is complementary to an mRNA codon.
An anticodon is carried by a tRNA.

8. Ribosomes consist of two subunits.
The large subunit has three binding sites for tRNA.
The small subunit binds to mRNA.

9. For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble.
(1) A complementary tRNA molecule binds to the exposed codon, bringing its amino acid close to the first amino acid.

10. (2)The ribosome helps form a polypeptide bond between the amino acids.
The ribosome pulls the mRNA strand the length of one codon.

11. (3)The now empty tRNA molecule exits the ribosome.
A complementary tRNA molecule binds to the next exposed codon.
Once the stop codon is reached, the ribosome releases the protein and disassembles.

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