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DNA, RNA and Protein
Synthesis
How Proteins Are Made and How
Are Your Traits Determined
through Gene Expression?
What are Proteins?
• Organic compounds contain C, H, O, N
•
Made of small units called amino acids-
building blocks of proteins
What are Proteins continued?
• Proteins are made at the ribosomes
• Ribosomes read the DNA message
on the mRNA and join amino acids
to make proteins
• Your body can make 12 of the 20 amino
acids, but the other 8 essential amino acids must
come from your diet
• Name food items that are good source of these
essential amino acids? (Hint: must come from
protein source).
Functions of Proteins
• Enzymes-catalyst
proteins used to control the rate
of chemical reactions (lower amount of energy
needed to start a reaction)
• Structural component of body: skin, hair, muscles, bone
Marcia S. Brose, M.D., Ph.D., Assistant Professor, Hematology/Oncology, The
University of Pennsylvania Cancer Center, Philadelphia, PA. Review provided
http://training.seer.cancer.gov/module_anatomy/unit4_1_muscle_functions.html
Functions of Proteins continued
• Some proteins are hormones and carry chemical
messages; for example insulin, regulates blood sugar
• Transport substances such as hemoglobin in RBC that
carries O2
http://www.accs.net/users/kriel/chapter%20seven
• Protect body against disease; antibodies of immune system
SO…how does a cell make
proteins anyway? And what does
this have to do with DNA and
RNA?
Let’s Review…
DNA
vs.
• Contains deoxyribose
sugar
• Is double stranded
• Bonds A-T and C-G
• Never leaves the nucleus
•
•
•
•
RNA
Contains ribose sugar
Is single stranded
Bonds A-U and C-G
Can leave the nucleus
Remember there are three
types of RNA
• mRNA: messenger RNA;
carries DNA message to
ribosomes
• tRNA: transfer RNA;
transfers amino acids to
ribosomes
mRNA
tRNA
towing
• rRNA: ribosomal RNA;
makes up ribosome-protein
factories of the cell
Protein
factory
Role of RNA
AGAT
• While DNA contains the
T C GA
instructions for making proteins G C A C
TC AT
in the form of genes…
• RNA is the molecule that
actually does all the work
of putting the protein
together
Overall Process of Protein Synthesis
(Gene Expression)
Transcription
DNA
Translation
mRNA
Transcription
Protein
•Information in DNA is “transcribed”
(rewritten) as a molecule of mRNA
Translation
•DNA information on mRNA is
“translated” into protein language
Enzymes
• There are two different enzymes necessary
in making a protein.
• Helicase – breaks hydrogen bonds
between nitrogen bases
• Polymerase – brings new nucleotides
and bonds them to existing strands
• What organic compound group do enzymes
belong to?
TRANSCRIPTION- First Process of
Protein Synthesis
•
Occurs in the nucleus
• Uses RNA Polymerase
• Makes mRNA from
DNA template
• 60 nucleotides are
copied per second
• Initiator (start) Codon: AUG
TRANSCRIPTION Steps
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
G
C
A
T
C
C
A
T
T
1. Helicase breaks
the hydrogen
bonds between
the nitrogen bases
A
TRANSCRIPTION
G
G
C
A
T
C
C
G
T
A
2. The DNA strands
break apart
T
A
TRANSCRIPTION
T
A
A
T
G
C
C
G
G
C
A
T
TRANSCRIPTION
T
A
A
T
G
C
C
G
G
C
A
T
TRANSCRIPTION
T
A
A
T
G
C
C
G
G
C
A
T
TRANSCRIPTION
T
A
A
T
G
C
C
G
G
C
A
T
TRANSCRIPTION
T
A
A
T
G
C
C
G
G
C
A
T
TRANSCRIPTION
T
A
A
G
C
C
T
G
3. RNA Polymerase
brings in mRNA
C
nucleotides and
matches them
with
their
DNA
G
complement.
A
T
G
G
C
T
A
G
C
C
G
T
A
A
T
A
A
G
G
C
T
G
C
C
G
T
A
A
T
A
A
G
G
C
C
C
T
G
C
G
T
A
A
T
A
A
G
G
C
C
C
T
G
C
G
G
T
A
A
T
A
A
G
G
C
C
C
T
G
C
A
A
G
G
T
A
T
A
A
G
G
C
C
A
A
G
G
T
C
T
G
C
T
U
A
U
T
A
A
A
T
G
G
C
mRNA
DNA
C
A
A
G
G
T
C
C
G
G
C
A
A
G
G
T
C
C
G
G
A
C
A
U
T
T
A
4. mRNA
breaks
away from
the DNA
strand and
goes to the
ribosome
A
A
G
G
C
C
A
A
G
G
T
C
T
G
C
T
A
U
A
A
G
G
C
C
A
A
G
G
T
C
T
G
C
T
A
U
A
A
G
G
C
C
A
A
G
G
T
C
T
G
C
T
A
U
U
A
A
T
G
G
C
C
A
G
A
T
C
G
G
C
T
A
To Ribosome
T
A
A
C
G
T
A
G
5. The DNA
strand is put
back
together
C
C
G
T
T
A
A
T
G
C
C
G
G
C
A
T
T
A
A
T
G
C
C
G
G
C
A
T
T
A
A
T
G
C
C
G
G
C
A
T
T
A
A
T
G
C
C
G
G
C
A
T
T
A
A
T
G
C
C
G
G
C
A
T
G
G
G
C
A
T
C
C
A
T
T
A
SUMMARY
Transcription
A
G
C
A
G
A
G
DNA
C
C
G
G
T
A
C
T
T
U
A
Translation
mRNA
tRNA
Protein
Some additional notes about making
mRNA…
• DNA contains many non-coding regions, also
known as “junk DNA”
• RNA is not made from the junk DNA
• Only 1 of the 2 DNA strands is used to make the
mRNA; this strand is called the DNA template
• DNA code on the mRNA is read three bases at
once, and these three letter base combinations
on the mRNA are called codons
• Codons determine your genetic code and the
traits expressed from protein synthesis