Protein
Synthesis
DNA & RNA at
Work
DNA/RNA Comparison
Characteristic
DNA
RNA
Number of Strands
2
1
Type of Sugar
Deoxyribose
Ribose
Letters Names of Bases
G, A, C, T
G, A, C, U
Cell Location
Nucleus
Nucleus, cytoplasm,
ribosome
Purpose
Duplication or replication
in order to make new cell
with the exact same traits
Sends signals to create
proteins
From Mrs G ~
1. DNA & RNA have some similarities, but in the end DNA is MUCH more complicated.
2. RNA cannot read thymine so it replaces it with uracil . This means that when RNA reads
the sections of DNA to make needed proteins the Ts become Us. The Us then compliment
As when pairing (T changes to U → and U will pair with A).
3. Also, look at the differences in location and purpose.
Making a Protein
1. In the nucleus, a mirror-like copy of the gene is made of
RNA. This copy is known as messenger RNA or mRNA. The
mRNA leaves through a pore in the nuclear membrane and
goes out into the cytoplasm.
2. Each group of 3 bases (a codon) codes for an amino acid.
The mRNA or RNA copy is then fed through a ribosome.
The ribosome then requests particular amino acids.
3. Transfer RNA (tRNA) molecules pick-up or gather amino
acids from the cytoplasm.
4. Transfer RNA (tRNA) molecules deliver amino acids back
from the cytoplasm to the ribosome.
5. The amino acids are dropped off at the ribosome and
joined to make a protein. One protein is usually produced
for each gene.
6. Proteins make traits.
From Mrs. G ~
1. The info in PINK is vital , the rest is to help you understand how a protein is synthesized
or made.
Parts 1 & 2 should look VERY familiar! The ONLY difference is DNA is not replicating.
Instead, RNA is forming on the DNA strands to copy the message.
Part 3 shows protein synthesis where mRNA goes out to find a ribosome, then tRNA
finds amino acids/codons (3 letter sets) to build long polypeptide chains/proteins.
From Mrs. G ~ Ok, let’s try it. You know how to do this part, you did it with your
DNA model…
DNA Replication
• DNA Strand: C
G
A
T
G
C
T
A
• DNA Strand: G
C
C
G
T
A
T
A
From Mrs. G ~ This is new, but you can do it! Once you have this down it is the
same patterns over and over.
Protein Synthesis
1.
2.
3.
4.
DNA Strand:
mRNA Strand:
tRNA Strand:
Amino Acid:
C
G
C
A
G
U
C
A
G
Glutamine
From Mrs. G ~
1. To find the mRNA strand, take the DNA strand and apply the complementary
base pair. Don’t forget that Ts become Us at this point .
2. For the tRNA strand apply the complementary base pair again. Ts are not
used here either.
3. Now look a the amino acid chart. Start on the LEFT side and work to the
RIGHT side. The first base here is C and it is the second letter down. Then for
the second base, move across to the middle section. Find the A in the third
column to the right. For the third base, simply stay in the block of four
amino acids and find the letter G to the right – that’s right you found
GLUTAMINE!
Protein Synthesis
1.
2.
3.
4.
DNA Strand:
mRNA Strand:
tRNA Strand:
Amino Acid:
T
G
A
A
C
U
U
G
A
Stop codon
Try again…See not too bad, right?
Protein Synthesis
1. The codons for Lysine could be?
A A A
or
A A G
2. The amino acid produced by UGC is?
Cysteine
Protein Synthesis
Challenge Problem…Can you work backwards?
Amino Acid produced in Tryptophan
1. tRNA Strand:
U
G
G
2. mRNA Strand:
A
C
C
3. DNA Strand:
T
G
G
