Protein Synthesis
How can DNA be used by the cell
to make a protein?
DNA Replication Review

Draw the complimentary strand of DNA
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GCT TAG ACT GGC
Where (in the cell) does replication occur?
What does it produce?
What are the 4 nitrogenous bases in DNA?
When in the cell does DNA replication occur?
Why does DNA need to double?
Importance of protein synthesis?
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Every inherited trait
is controlled by one
or more proteins.
Protein synthesis is
the process that
makes these
proteins.
Fill It In …
What is a trait?
How are the terms “protein” and “trait”
related?
Importance of protein synthesis?

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Each cell must produce
different proteins based on
the function of that cell.
For example, only blood
cells need to produce the
protein hemoglobin.
Central Dogma of Biology

The central axis
around which all
other biological
concepts rotate.
Central Dogma of Biology

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DNA structure controls
the production of
proteins.
A section of DNA which is
used as the blueprint or
code for the production of
a protein is a gene
Central Dogma of Biology

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Each gene is composed of a
specific sequence of
nucleotides.
This sequence can be
represented by writing the
order of nitrogen bases.

For example,
ACGCCATGCTAC
Central Dogma of Biology
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Every three bases in this
sequence is called a codon.
A codon is like a single word
in a sentence.
Only by putting the words
(codons) in the correct order
can you create a meaningful
sentence (protein)
Central Dogma of Biology

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Proteins are made of
amino acids.
Each codon directs the
cell to place a specific
amino acid in a particular
position as the protein is
built.
Central Dogma of Biology

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For example, the
codon CAA in DNA
codes for the amino
acid “valine”.
If this codon was the
third codon in a
gene, valine would
be the third amino
acid in the protein.
DNA:
TAC GGT CAA AAA
met
pro
val
phe
Central Dogma of Biology

Diagram of the Central Dogma
DNA
RNA
(transcription)
Protein
(translation)
Fill It In …
Three DNA nucleotides makes a ______.
One codon controls the placement of one
_______ _______.
Many amino acids make a _________.
Fill It In …
Rewrite the “Central Dogma” as a
sentence (use all of the words!)
Process of protein synthesis

Transcription
rewrites the DNA
code as messenger
RNA.
Process of protein synthesis

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DNA cannot leave the
nucleus (it is far too big)
to go to the ribosomes
where proteins are made.
Thus, it must send the
instructions using RNA.
Process of protein synthesis
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mRNA copies the DNA
when the DNA unzips
one sections called a
gene.
One gene makes one
protein.
Process of protein synthesis

messenger RNA is
constructed one
nucleotide at a time
using one side of
the DNA as a
template
Process of protein synthesis
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All RNA has a different
sugar (ribose) which
cannot bond to thymine.
Thus, RNA must use a
different nitrogen base
(uracil) as a substitute
for thymine.
Process of protein synthesis
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For example, if the
DNA side read CTA,
the mRNA would
read GAU.
DNA:
mRNA:
CTA
GAT
GAU
Process of protein synthesis

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mRNA leaves the nucleus
through a small opening in
the nuclear membrane
called a pore.
The DNA rezips the gene.
From RNA to
Protein Synthesis
Fill It In …
How does transcription produce a “script”
based on DNA?
Fill It In …
Highlight the mRNA.
Explain the diagram.
DNA
mRNA
mRNA
Cytoplasm of
cell
Nucleus
Transcription
happens in the
nucleus. An RNA
copy of a gene is
made.
Then the mRNA
that has been made
moves out of the
nucleus into the
cytoplasm
Once in the
cytoplasm, the
mRNA is used to
make a protein
Amino Acids
Protein
How does mRNA tell the cell what to do?
•mRNA is a message that codes for a protein
•Proteins are made in the cytoplasm and then work to
keep the cell alive
•Translation (protein synthesis): Process of making a
protein
•Proteins are made up of amino acids (small building
blocks)
•There are 20 different types of amino acids
Process of protein synthesis
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Translation uses
the mRNA to build a
protein.
Process of protein synthesis
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In the cytoplasm of the
cell, translation occurs at
the ribosome.
Ribosomes are made of
rRNA (ribsomal RNA)
and proteins.
Process of protein synthesis
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The mRNA “start” codon
(AUG) attaches to the
ribosome.
The ribosome holds
mRNA in place and helps
link amino acids together
to make a protein.
Process of protein synthesis

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tRNA (transfer RNA) is a
molecule that carries an
amino acid to the ribsomes.
In order for the tRNA to leave
the amino acid at the
ribosome, it must bond with a
codon on the mRNA.
Process of protein synthesis

The ribosome
allows the tRNA
anticodon (made of
three bases at the
bottom of each
tRNA) and the
complementary
mRNA codon to
pair.
Process of protein synthesis

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The amino acid is
removed from the tRNA
by an enzyme.
As each new amino acid
arrives on the tRNA,
amino acids are bonded
together IN ORDER by a
peptide bond to form a
polypeptide.
Process of protein synthesis

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When the ribosome reaches
a “stop” codon, it releases
the mRNA and the string of
amino acids separately.
The string of amino acids
folds and coils to shape the
protein.
Fill It In …
How does translation “read” the “script”
produced in transcription?
Fill It In …
Highlight the protein.
Explain this diagram.
Result of protein synthesis

Cells respond to
their environment by
producing different
types and amounts
of protein.
Result of protein synthesis

The cell produces
proteins that are
structural (forming part of
the cell materials) or
functional (such as
enzymes, hormones, or
chemicals for cell
chemistry)
Fill It In …
What is the END RESULT of protein
synthesis?
Result of protein synthesis
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All of an organism’s
cells have the same
DNA, but the cells
differ based on the
expression of the
genes.
Result of protein synthesis
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Multicellular
organisms begin as
undifferentiated
masses of cells.
Variation in DNA
activity determines
cell types.
Result of protein synthesis
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Different types of cells
expressing different
genes leads to
differentiation.
Only specific parts of
DNA are activated in
those cells.
Result of protein synthesis
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Once a cell
differentiates, the
process cannot be
reversed.
For example, we
have muscle cells,
nerve cells, and
others.
On Epigentics
Result of protein synthesis

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Gene regulation is the
process which determines
which genes will be
expressed (used to make a
protein).
This can be affected by the
cell’s history and/or
environment (g+e=p)
Proteins may be overproduced,
underproduced or produced at
incorrect times

Ex: injury repair or
cancer
Fill It In …
If gene regulation were not possible,
would cell specialization happen?
Why/why not?
Result of protein synthesis
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Each individual is a sexually
reproducing population has slightly
different sequences of nucleotides in
DNA when compared to other organims
of the same specie.
The different sequences lead to
different proteins, which produce
different traits (i.e. variation)
For example, two humans with different
eye color
Check Yourself!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
What controls inherited traits?
What controls the production of proteins?
Define a gene.
Diagram the central dogma of biology.
What is the purpose of transcription?
What type of RNA is used in transcription?
What nitrogen base in RNA is used as a substitution
for thymine?
What is the purpose of translation?
What two types of RNA are used only in translation?
What type of bond links amino acids.
Check Yourself!
1.
What controls inherited traits?
ONE OR MORE PROTEIN
Check Yourself!
2.
What controls the production of proteins?
PROTEIN SYNTHESIS OR DNA
Check Yourself!
3.
Define a gene.
A SECTION OF DNA THAT CODES FOR A
SPECIFIC TRAIT OR PROTEIN
Check Yourself!
4.
Diagram the central dogma of biology.
Check Yourself!
5.
What is the purpose of transcription?
TO MAKE A COPY OF DNA
Check Yourself!
6.
What type of RNA is used in transcription?
mRNA OR MESSENGER RNA
Check Yourself!
7.
What nitrogen base in RNA is used as a substitution
for thymine?
URACIL
Check Yourself!
8.
What is the purpose of translation?
TO PRODUCE A PROTEIN
Check Yourself!
9.
What two types of RNA are used only in translation?
rRNA OR RIBOSOMAL RNA AND
tRNA OR TRANSFER RNA
Check Yourself!
10. What type of bond links amino acids.
PEPTIDE BOND
Let’s practice …
DNA: TAC AAT CGC
mRNA:
a.a.:
DNA: TAC GCG ATT
mRNA:
a.a.:
Process of Translation
•mRNA moves out of
nucleus and into
cytoplasm
Nucleus
Cytoplasm
•mRNA attaches to a
ribosome
•Transfer RNA (tRNA)
decodes the mRNA and
brings amino acids to build
up the protein
tRNA
Amino
acid
Anticodon (3 bases on
tRNA): Matches up to
codons on mRNA
•Protein (chain of amino acids)
detaches from ribosome and
goes off to work in the cell
Ribosome