Download Translation Notes

Translation
What is Translation?
• Translation converts the information in the
mRNA into a sequence of amino acids that
make up a protein.
Where does Translation happen?
• Translation takes place
in the cytoplasm of the
cell.
• Takes place in both
prokaryotic and
eukaryotic cells.
REVIEW
• Proteins:
–Involved in movement, eyesight,
digestion, etc.
–Long chain of many amino acids
–Proteins differ in the number and order
of amino acids.
Review
• Amino Acids:
– Molecules that contain carbon, hydrogen, oxygen
and nitrogen (sometimes sulfur)
– CHON
– Organisms use 20 different amino acids to build
proteins
– Your body makes 12, others come from food you eat
• Amino acids are linked by peptide bonds.
• Amino acids interact to give a protein its shape.
• Incorrect amino acids change a protein’s structure
and function.
Translation…
• Amino acids are coded
by mRNA base
sequences.
• Three bases on mRNA
make up a triplet-A
codon is a sequence of
three nucleotides that
codes for an amino
acid.
codon for
methionine (Met)
codon for
leucine (Leu)
Genetic Code…
used to determine
what amino acid
a codon
encodes for.
Codons
• One START codon-AUGwhich codes for
Methionine.
– Signals the start of
translation.
• Three STOP codons:
UAA, UAG, and UGA.
– Signal the stop of the
amino acid chain.
Reading Codons
• A change in the
order in which
codons are read
changes the protein
that is made.
• Regardless of the
organism, codons
code for the same
amino acid.
Anticodon=tRNA
• An anticodon is a
set of three
nucleotides that is
complimentary to
a mRNA codon.
• An anticodon is
transported by a
tRNA.
Practice…Match the Codon to its
correct Anticodon.
Codon: CUG
Anticodon:
Codon: GCA
Anticodon:
Codon: AUG
Anticodon:
Ribosome Structure
• Ribosomes consist of two subunits.
– The large subunit has three binding sites for tRNA.
– The small subunit binds to mRNA.
How does Translation happen?
• STEP 1: The ribosome assembles on a start
codon (AUG) of mRNA strand. An anticodon,
or tRNA, matches up with the codon on the
mRNA strand.
Translation: Step 1
How does Translation happen?
• STEP 2: The ribosome forms a peptide bond
between the amino acids while breaking the
bond between the previous amino acid and its
tRNA. The ribosome pulls the mRNA strand
the length of one codon. The first tRNA exits
the ribosome, and another codon is exposed.
Translation: Step 2
How does Translation happen?
• STEP 3: The now empty tRNA molecule exits
the ribosome. A complementary tRNA molecule
binds to the next exposed codon.When the
ribosome encounters a stop codon (UAA, UAG,
UGA), the ribosome falls apart and the protein is
released.
Translation: Step 3