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Protein Synthesis
Transcription and Translation
Protein Synthesis
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Is the formation of the proteins
using information coded on DNA
and carried out by RNA
STEP 1
RNA Transcription
STEP 2
RNA Translation
DNA
RNA
Proteins
Protein
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Each protein molecule is made up of
one or more polypeptides.
Each polypeptide is made up of a
sequence of amino acids.
There are 20 different types of Amino
Acids.
Amino Acids
Polypeptides
Proteins
Genetic Code
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System that contains information
needed for proper cell functioning.
This information is built into the
arrangement of nitrogen bases.
Codon
A specific group of three sequential bases on
mRNA.
 Each codon codes for a specific amino acid.
There are 64 possible codons. Coding for amino
acids is universal for all animals.
 See Codon chart on Page 207
 What does the following mRNA code for?
AUG UUU CCU CAA GGU GAG GCG ACA UAA
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Transcription
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First step in protein synthesis
Occurs in the nucleus
End result is RNA molecule with a
complementary base sequence to DNA.
Flow of Genetic Information
DNA
RNA
RNA TRANSCRIPTION
STEP 1
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Enzyme called RNA Polymerase binds
to DNA molecule at the promoter
Promoter is a sequence of nucleotides
on a DNA molecule where transcription
will begin
Once RNA polymerase binds to the DNA
molecule it will unwind and separate the
two complementary DNA strands.
RNA TRANSCRIPTION
STEP 2
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RNA polymerase adds free RNA nucleotides that are
complementary to the nucleotides on one of the DNA
strands.
They will attach by hydrogen bonds and form a strand on
messenger RNA.
RNA polymerase will also establish the sugar to
phosphate bonds between the nucleotides in the new
mRNA strand.
As the RNA Polymerase passes the separated DNA
strands rewind.
RNA TRANSCRIPTION
STEP 3
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The enzyme will reach a pattern of bases on the
DNA strand that signals termination.
The enzyme will stop and release the new RNA
strand.
The new RNA strand now moves to the
cytoplasm
End Result of Transcription
Transcription just created a RNA molecule
with a complementary base sequence to
DNA.
Each type of RNA molecule (tRNA, mRNA,
rRNA) is made this way and will start their
job in protein synthesis.
RNA TRANSCRIPTION
PRACTICE PROBLEM:
Transcribe a mRNA molecule from the
following DNA Strands.
DNA: TAC ATA TAA CGC CCG AGC TGC GGC
Warm Up:
Transcribe a mRNA molecule from the
following DNA Strands.
AGG TTA GGC CCG ATA AGC GCG GGC
Today:
Homework:
TRANSLATION
The process of assembling protein
molecules from information encoded in
mRNA.
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Second Step in Protein Synthesis
This process uses all three types of RNA
Process occurs in the cytoplasm
Transfer RNA (tRNA)
Transfer RNA (tRNA) bears a sequence of
three bases called the Anticodon.
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The anticodon base sequence is
complimentary to the codon on the mRNA
tRNA carries an amino acid to the
ribosome's
mRNA and tRNA will pair together during
translation.
TranslationSTEP 1 INITIATION
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Process starts when mRNA migrates out
of nucleus by nuclear pores, and
migrates to the ribosome's.
Amino acids floating freely in the
cytoplasm are transported to the
ribosome's by the tRNA
STEP 1
INITIATION (CONT)
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The assembly of polypeptides start when
the ribosome's attaches to the AUG(start)
codon of the mRNA
The AUG codon pairs with the anticodon
UAC on a specific tRNA
Methionine is usually the first amino acid
(not always the first in the amino acid
chain because it may be removed)
STEP 2 & 3 ELONGATION
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The Polypeptide chain is put together.
Ribosome's moves along the chain and decodes
the mRNA and attaches the amino acids together
by peptide bonds.
The tRNA will bring in the next amino acid, pair
up with the codon on the mRNA and attach the
next amino acid together
STEP 4 TERMINATION
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Eventually the ribosome reaches a stop codon and
the process comes to the end
The new polypeptide is complete and released.
Ribosome's may be working at different parts of the
mRNA simultaneously.
STEP 5 DISASSEMBLY
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The components of translation separate.
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The last tRNA leaves.
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The Ribosome leaves the mRNA
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The translation machinery are now ready
to translate another mRNA
Translation Practice
DNA: TAC ATA TAA CGC CCG AGC TGC GGC
mRNA:
Amino Acid Chain: