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Unit #4
Dry-Lab: Translating Genetic Information
Background: Genetic information encoded in DNA molecules will ultimately be expressed
in the form of the protein molecules produced by cells. In this dry-lab, you will be working
with two such proteins, somatostatin (a hormone which regulates the rate at which
nutrients such as glucose are absorbed by the digestive tract) and beta hemoglobin (one of
the components of the pigment molecule, hemoglobin, found in red blood cells). You must
work logically and carefully! Small mistakes can make a big difference.
Materials:
Adding machine tape (if available)
mRNA/Codon chart
Colored pencils
Part I:
Procedure:
1.
Below you will find the 5’ to 3’ strand of DNA which codes for the hormone
somatostatin, which is produced by the pancreas.
5’ ATG GCT GGT TGT AAG AAC TTC TTT TGG AAG ACT TTC ACT TCG TGT TGA
TAG 3’
2.
Using the above strand as a template, determine what the 3’ to 5’ base
sequence would be. Write the 3’ to 5’ base sequence on your adding machine
tape. Label it to show that this is the 3’ to 5’ strand.
3.
The 3’ to 5’ strand is the coding strand for somatostatin. Label each strand as
“coding” or “non-coding”. Using the coding strand, determine what the mRNA
base sequence would be and write it below the 3’ to 5’ strand on the adding
tape. Label it to show that this is mRNA.
4.
Using the mRNA codons listed on the adding tape, and using a codon table,
determine which amino acids are coded by each mRNA codon. Write them
under each codon, using a different color pencil. Label this line as Amino
Acids.
5.
On a separate sheet of paper, answer the following questions:
a. What is another name for the 3’ to 5’ strand of DNA?
b.
What is the name of the process you performed in #2? (Replication,
Transcription, Translation?)
c.
What is the name of the process you performed in #3? (Replication,
Transcription, Translation?)
d.
What is the relationship between the nitrogen bases in #2 and the
nitrogen bases in #3?
e.
What is the name of the process you performed in #4? (Replication,
Transcription, Translation?)
f.
When the amino acids in #4 are bonded by peptide bonds, what is the
name of the polypeptide they form?
Part II:
Procedure:
1.
Normal beta hemoglobin is called hemoglobin A, while the hemoglobin that
creates sickle cell anemia is called hemoglobin S. Below you will find the amino
acid sequence for the first 8 amino acids for beta hemoglobin. The first
sequence is for normal hemoglobin A. The second sequence is for hemoglobin
S—the hemoglobin responsible for sickled cells. (Note: Consistency is
important. Match the mRNA codons for glutamate and valine as closely as
you can!)
Normal hemoglobin A:
Sickled hemoglobin S:
val-his-leu-thr-pro-glu-glu-lys
val-his-leu-thr-pro-val-glu-lys
2.
Turn your adding machine tape over, and using a codon table, write out the
mRNA codons that code for each of the amino acid sequences above.
3.
Circle the amino acids that are different in the two sequences.
4.
How many nitrogen bases are different in the two sequences?
Code for glutamine:
Code for valine:
Number of different nitrogen bases:
5.
Is it possible for the mutation (change) of a single nitrogen base to cause
genetic problems? Explain.
6.
Is it possible for the mutation of a single nitrogen base to cause no change in
amino acid sequence? (Look at your mRNA coding chart and give an example
where the change of a single nitrogen base would have no effect on the amino
acid produced.)
7.
The mutation that causes sickle cell anemia is called a “point mutation”. Why
is that an appropriate term?
WHEN YOU ARE FINISHED, STAPLE YOUR ADDING TAPE TO THIS PAPER AND
HAND BOTH IN.