Protein Synthesis
From Codes/genes to Proteins/machines
Central Dogma- DNARNAProtein
It explains how genetic information flows
Can you break the code???
8 5 12 12 15
3 12 1 19 19
Making Proteins
Protein Synthesis
Process of making
proteins
Two part process
1. Transcription
2. Translation
Remember Reading DNA?
The four chemical bases in
DNA (A, T, C, G) create a
code/gene
Ribosomes “read” this DNA
code/gene to make proteins.
Where are ribosomes
located?
Where is DNA located?
Nucleus Problem
Nucleus not permeable to DNA
DNA is a large to fit out of pore
Double stranded = wide
How do we get the code/gene
to the ribosomes to make
proteins?
Copy code into a smaller
molecule
RNA (ribonucleic acid)
RNA vs DNA
• What is the difference?
• Compare and contrast
DNA to RNA
DNA
BOTH
RNA
Two Types of Nucleic Acids
Deoxyribonucleic Acid
Ribonucleic Acid
DNA
RNA
Double Stranded
Single Stranded
Smaller
Nucleotide sugar =
Nucleotide sugar =
Deoxyribose
Ribose
Bases = A, T, G, C
Bases = A, U, G, C
The Tail of Two RNA’s
Two RNA types needed for Protein synthesis
mRNA
messenger RNA
tRNA
Transfer RNA
Protein synthesis
Step 1: Transcription
 Process of making messenger RNA (mRNA) from
DNA
 Exactly like Replication (with one small difference)
Use base paring rules
C pair with G
G pair with C
T pairs with A
BUT
A pairs with U (uracil)
Which enzyme is used to add nucleotides??
Modifications of Mrna before it can leave nucleus
Add5’ cap- protects mRNA and allows it to leave nucleus/find a
ribosome
Poly (A) tailThey are added to: protect mRNA and allow it to leave nucleus/find a
ribosome
Introns (non-coding sequences between exons) are removed and exons
(amino acid coding sequences) are spliced together
mRNA Function
Take gene from nucleus to ribosome
Disposable copies(often thoughsands)
of VERY important information
Tells Ribosome how to build protein.
Transcription Practice
(DNA to mRNA)
Cheat Sheet
A=U
T =A
C=G
G =C
Open DNA:
A T G C C G T T A A C G A G T C T
mRNA copy:
U
Step 2: Translation
What does it mean to Translate something?
Change from one language to another
Biology Translation
To go from the language of DNA (A, T, C,
G, and U) to the language of protein
(amino acids)
Amino acids are the building blocks of
proteins
Translation
Involves ribosome, mRNA and tRNA (transfer RNA)
Ribosome reads mRNA on codon (3 bases) at a time
tRNA matches with codon on mRNA
Brings amino acid with
Ribosome takes amino acid from tRNA and links it to
growing protein
Translation summary
mRNA read by ribosome in
groups of 3 bases called
CODONS
Ex: AUG = Start making protein
Ex: UGA = Stop making
protein
Codon on mRNA match Codon
on tRNA
Codon tells ribosome what
amino acid to attach to protein
Decoding mRNA
Humans use decoder
Codon wheel
Codon chart
Reading Codon Wheel
Using 3 base Codon
Start at center of the wheel
Find the first nitrogen base in codon
Sets what ¼ of circle you will work in
Move to the next ring of circle
Find second nitrogen base
Sets what ¼ of the remaining circle you are in
Move to the last ring
Find third nitrogen base
Arrive at your amino acid
Finding
Amino acid
for Codon
GAG
Reading Codon Chart
Using 3 base Codon
Start at left side
Find the first nitrogen base in codon
Sets what row you are using
Move to the top of chart
Find second nitrogen base
Sets what column you are using
Find where column and row meet
This is the box you are working in
Find matching Codon in this box
Find the
amino acid
for the codon
CGU
CYU
Transcribe this DNA to mRNA
Translate the mRNA to amino acids
DNA
mRNA
Amino
Acid
T
A
C
G
G
C
A
T
C