Translation

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Transcript Translation

Translation: RNA to Protein Objectives
• Trace the path of protein synthesis.
Review: One Gene One Polypeptide
• DNA  RNA  Polypeptide
• The DNA sequence for a gene is transcribed
into a single-stranded RNA molecule.
• The mRNA takes the message to the site of
protein synthesis.
Translation: From mRNA to Protein
• Translation: The process of converting the
information in mRNA into a sequence of
amino acids in protein.
• Translation occurs at the ribosomes.
• Based on a three-base code.
The Codon
• Three-base
sequence that
codes for one
amino acid.
• 3 bases : 1
amino acid.
Translating the Code
• Read from the mRNA
sequence.
• AUG = Met (start)
• GCG = Ala
• UGA = stop
• Translation requires
transfer RNA (tRNA).
Transfer RNA
• tRNA translates the triplet code of mRNA into
the amino sequence.
• Anticodon: the three
bases on tRNA that are
complementary to the
mRNA codon.
• Carries a specific amino
acid.
Ribosomes
• Site of translation
• Coordinates the
functioning of mRNA
and tRNA.
Translation
Translation
Translation
Translation
Translation
1. Describe what happens as the ribosome moves along the mRNA
strand.
Amino acids are added to the growing polypeptide chain
until a stop codon is reached.
Translation
2. What is the relationship between mRNA and the completed
polypeptide?
The sequence of codons in mRNA determines which amino
acids compose the polypeptide and in what order.
Translation Animations
Simple Animation
www.dnai.org animation
Translation: A Review
• Translation converts the mRNA code into the
amino acid sequence of proteins.
• Translation occurs at the ribosomes and uses
tRNA.
• tRNA carry specific amino acids and posses
an anticodon which is complementary to the
mRNA codon.
Translation: A Review
• At the ribosome, tRNA bring in their amino
acids according to codon-anticodon pairing.
• The amino acids bond together to form
polypeptides.
• The polypeptide chain grows longer as new
tRNA molecules are brought in and the
“used” tRNA molecules move out.
Translation: A Review
• The process occurrs until a stop codon is
reached.
• The final product is a unique polypeptide
whose amino acid sequence corresponds to
the nucleotide sequence of mRNA, and
ultimately, DNA.
Question 1
What is the role of the ribisome in protein
synthesis?
Answer
The ribosome binds to mRNA and tRNA and
assembles the amino acids in the order
needed for the protein to be synthesized.
Question 2
What is an anticodon, and what does it
represent?
Answer
An anticodon is a sequence of three
nucleotides on the tRNA molecule that binds
to a codon of the mRNA strand.
Question 3
What happens when a stop codon is reached
during translation?
Answer
When a stop codon is reached, translation
ends and the amino acid strand is released
from the ribosome.
Question 4
What amino acid
is coded for by
the mRNA codon
CAU?
Answer
His
Question 5
What amino acid
is coded for by
the DNA
sequence CAT?
Answer
Val
Question 6
What anticodon would bond to the mRNA
codon GAC?
A. CTG
B. CUG
C. GAC
D. GUC
The answer is B.
Translation: RNA to Protein Objectives
• Describe the structure and function of
DNA and its role in DNA replication.