8.5 Translation
KEY CONCEPT
Translation converts an mRNA message
into a protein.
8.5 Translation
Translation converts mRNA messages into proteins.
• A reading frame is a series of three non-overlapping
nucleotides read, in order, by a cell
• A codon is a sequence of three nucleotides that codes for
an amino acid.
• A codon must be read in the correct reading frame for the
correct protein to be made.
Start codon for
codon for
• The start codon is
methionine (Met)
leucine (Leu)
– AUG
8.5 Translation
• A change in the order in which codons are read changes
the resulting protein.
• There is a “common language”: Regardless of the
organism, the same codons code for the same amino
acids.
8.5 Translation
• The genetic code matches each codon to its amino acid or
function.
– one start
codon (AUG)
codes for
methionine
– three stop
codons(UAA,
UAG, UGA)
codons
The genetic code matches each RNA codon with its amino acid or function.
8.5 Translation
Amino acids are linked together to become a protein.
• An anticodon is a set of three nucleotides on a tRNA that
bind to a complementary mRNA codon.
• A tRNA (transfer RNA) carries amino acids from the
cytoplasm to the ribosome
8.5 Translation
• Ribosomes (yes, the organelles in the cytoplasm and the
“rough stuff” on the rough E.R.) make proteins!
– The large ribosomal subunit has 3 binding sites for tRNA.
– The small ribosomal subunit binds to mRNA.
3.
6.
8.5 Translation
• 1. For translation to begin:
– tRNA binds to a start codon and signals the ribosome to
assemble.
– A complementary tRNA anticodon binds to the exposed
codon, bringing its amino acid close to the first amino
acid.
8.5 Translation
2. The ribosome helps form peptide bonds between the
amino acids.
3. The ribosome pulls the mRNA strand the length of one
codon AND…………………..
8.5 Translation
– The now empty tRNA molecule drops off the ribosome.
– A complementary tRNA anticodon binds to the next
exposed codon.
– Once the stop codon is reached, the ribosome
releases the protein and disassembles.
4. tRNA
1. Amino acid
2. Peptide bond
5. Reading frame
8. anticodon
7. mRNA