Names: ________________________________________________ Block: _____ Date:_____________
Protein Synthesis Modeling Lab
Chromosomes are found in each cell of all living organisms. Obviously, chromosomes must be important. But, what
is a chromosome? Each chromosome is composed of a series of genes. Each gene directs the formation of a specific
protein.
Chemically, chromosomes (and therefore genes) are made up of DNA (deoxyribonucleic acid). One single DNA
molecule makes up a chromosome. The series of nucleotides which make up the DNA provides the key to “reading
the genes.”
Procedure:
Part A. “Language” of Genetics
Take out the yellow DNA nucleotides only.
The order of DNA bases acts as a code. This code determines the sequencing of the amino acids that
make a protein. Every 3 bases is a codon for 1 amino acid.
Example codon: TTC = lysine
Three of the codes do not code for amino acids. These are “stop” codes to indicate the end of the gene.
1. Construct the following sequence with the nucleotide models: ATAACG.
2. Identify the 1st in your sequence codon:_____Identify the 2nd codon in your sequence:____
3.
Use Table I below to determine which two amino acids your DNA sequence codes for.
List these two amino acids:
Table I
Amino Acid
Alanine (ala)
Arginine (arg)
Asparagine
(asn)
Aspartic acid
(asp)
Cysteine (cys)
Glutamine
(gln)
Glutamic acid
(glu)
Glycine (gly)
Histidine (his)
Isoleucine
(iso)
Leucine (leu)
DNA Code
CGA CGG CGT CGC
GCA GCG GCT GCC
TCT TCC
TTA TTG
CTA
CTG
Amino Acid
Lysine (lys)
Methionine
(met)
Phenylalanine
(phe)
Praline (pro)
ACA
ACG
Serine (ser)
GTT
GTC
CTT
CTC
Threonine
(thr)
Tryptophan
(try)
Tyrosine (tyr)
Valine (val)
Stop
CCA CCG
GTA GTG
TAA TAG
CCT CCC
TAT
GAA GAG GAT GAC
AAT AAC
DNA Code
TTT TTC
TAC
AAA
AAG
GGA GGG
GGT
GGC
TCA TCG AGA AGG
AGT AGC
TGA TGG TGT TGC
ACC
ATA
CAA
ATT
ATG
CAG CAT CAC
ATC ACT
4. Using Table I, list a different DNA sequence that would code for the same two amino acids.
5. How many amino acids are listed in Table I? (The stop codon is not an amino acid.)
6. How many DNA codes are listed in Table I?
7. Do some amino acids have more than one DNA code?
8. Analogy: Create an analogy that compares DNA to the English language. (Hints: identify the
letters, words etc.).
Part B. THE HEMOGLOBIN GENE
9. Hemoglobin is the red blood cell protein which is responsible for oxygen transport. The
amino acid sequence for a portion of the hemoglobin protein is:
Table II
...proline, glutamic acid, glutamic acid, lysine…
How many DNA nucleotides would it take to code for the four amino
acids above? Explain your answer.
Amino Acid
alanine
DNA code
CGT
glutamic acid
CTC
lysine
TTC
proline
GGA
10. Use Table II to write the nucleotide sequence which codes for
valine
CAC
these four amino acids in the Hemoglobin protein (...proline,
glutamic acid, glutamic acid, lysine ...). Write the code from left to right. Directly below this
coding strand sequence indicate the bases which would form the other half of the DNA ladder.
coding strand: ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___
complementary strand: ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___
11. Use the model pieces to construct the DNA coding strand for this portion of the
hemoglobin gene. Then construct the complementary strand. The two strands should be
together (the coding strand on top and the complementary strand on bottom.)
12. The entire hemoglobin molecule is made up of 146 amino acids. The nucleotides which code
for the 146 amino acids of the hemoglobin protein are called the hemoglobin gene. Each gene
codes for a particular protein. How many nucleotides would it take to construct the coding
strand of the hemoglobin molecule?
13. How many nucleotides would it take to make a model of this part of the DNA molecule?
14. Do you think this strand of nucleotides represents an entire chromosome or just part of
one? Explain your answer.
Part C. Transcription and Translation
DNA does not code directly for amino acids. The linking up of amino acids to form the protein
occurs in the cell cytoplasm. DNA remains in the nucleus. You will now explore the way a DNA
molecule transfers its information from the nucleus to the cytoplasm where proteins are created.
This process is call transcription. In addition to DNA, the cell contains another type of nucleic acid,
RNA (ribonucleic acid). RNA is also made up of nucleotides but RNA nucleotides differs slightly
from DNA nucleotides
15. Compare the blue messenger RNA (mRNA) models with the yellow DNA nucleotides. List
the two differences.
Separate the two strands of your DNA model of the hemoglobin gene segment. Using the coding side
(top) of your DNA model as a pattern, pair the correct mRNA nucleotides with this DNA half.
16. List the sequence of this mRNA strand.
17. What combinations of nucleotides form a RNA-DNA pair?
DNA Base
_______
_______
_______
_______
RNA Base
_______
_______
_______
_______
Slide the mRNA strand away from the DNA. Keep the mRNA strand in order.
Reform your double strand of DNA.
This single mRNA strand now contains the DNA message. It is called messenger RNA (mRNA). In
the cell, mRNA moves from the nucleus into the cytoplasm. This process is called translation. The
mRNA is used as the pattern for protein synthesis.
DNA  mRNA
Another type of RNA is found in the cytoplasm, transfer RNA (tRNA). A tRNA molecule has two
important regions: one pairs with mRNA and the other combines with a specific amino acid. A
tRNA molecule at the end opposite the three bases of the tRNA that pair with the mRNA.
Take out the tRNA molecule models (green) and the amino acid models (pink), You now have the
mRNA, tRNA and amino acids necessary to make a protein. You will use these models to make a
portion of the hemoglobin protein.
Place the correct amino acid with its tRNA. Now, using the information on the mRNA strand, place
the tRNA molecules in the proper places along the mRNA.
18. Fill in the blanks for your model (one example is given).
mRNA
tRNA
CCU
GGA
Amino acid
pro
Remove the mRNA and tRNA's.
19. List the sequence of amino acids you have constructed:
_________
_________
_________
_________
20. How does your sequence of amino acids compare to the sequence from
Part B?
Congrats! You have now modeled the process of Protein Synthesis.
Protein Synthesis Summary