Translation
The mRNA leaves the nucleus and travels to the ribosome.
Translation
• Purpose: To use the
information in the
mRNA sequence to
make proteins.
• Location: At the
ribosome (ribosomes
are made of rRNA).
http://www.youtube.com/watch?v=Ikq9AcBcohA
Translation
Process:
• The ribosome reads the mRNA 3
nucleotides at a time.
• Codon: a group of 3 mRNA
nucleotides that corresponds to a
single amino acid.
• Genetic Code: The sequence of
nucleotides in DNA or RNA that
determines the specific amino
acid sequence in the synthesis of
proteins.
tRNA
molecules
Growing
polypeptide
Large
subunit
mRNA
Small
subunit
http://www.youtube.com/watch?v=5bLEDd-PSTQ
Translation
• Genetic Code
– There are 64 different
codon combinations
(4 X 4 X 4 = 64).
– There are only 20 different
amino acids, so there is
more than one codon for
each amino acid.
– Methionine is always the first amino acid in a protein.
(AUG is referred to as a start codon)
– There are three different stop codons which end
translation.
So if you give me a sequence of DNA can I figure out
the exact sequence of amino acids?
STEPS
1. Take the DNA and transcribe it into mRNA
Example:
mRNA:
TAC ATA CTA GCG ACT
AUG UAU GAU CGC UGA
2. Take the mRNA sequence and decode it
using the codon chart.
AUG = MET
UAU = TYR
GAU = ASP
CGC = ARG
Translation
• Using the genetic code, the tRNA
molecule brings the correct
amino acids to the ribosome.
• Each molecule of tRNA has 2
parts.
– Anticodon: sequence of 3
nucleotides that matches up
with an mRNA codon.
– Amino acid: each tRNA
molecule can bind to only a
specific amino acid.