The Coding of Protein Molecules By D.N.A.  

Glenn, Georgia S.                      Bogan High School
2231 W. 80th Street                    838-5080 
Chicago, Illinois, 60620
776-0341

Objectives:

Use paper models to demonstrate how DNA controls protein 
synthesis.

Use paper models to show the role of mRNA in protein synthesis.

Use paper models to show the role of tRNA in protein synthesis. 

Apparatus needed:

Paper models to represent the following molecules: 5 deoxyribose 
thymine, 5 deoxyribose adenine, 1 deoxyribose cytosine, 1 deoxyribose 
guanine, 3 ribose uracil, 2 ribose adenine, 1 ribose cytosine, 2 tRNA 
molecules, 2 amino acid molecules.  Cut out models beforehand and 
place in an envelope.  Print the DNA Neucleotide sequence A,A,T,A,G,T 
on the envelope.  Prepare a large "place mat" on which to assemble 
your protein molecule.  Construct by taping two large sheets of 
construction paper together.  Represent the nucleus by drawing a half 
circle on the left edge of your "place mat".  Make it wide enough to 
accommodate a double strand of nucleotides.  Make several circles to 
the left of the half circle to represent a few ribosomes in the 
cytoplasm. 
               
Strategies:  

Remove the puzzle pieces from the envelope.  On the "place mat", start 
at the left edge inside the red half circle, arrange your DNA 
nucleotides in the linear sequence written on the envelope.  Attach 
the corresponding nucleotides to make the right side of the DNA 
ladder. (Place the results on the board) 

Unzip the six nucleotides from the right half of your molecule.

Attach the appropriate ribose nucleotides to the left half of your 
DNA nucleotides.  (Record results on the board)

Slide the ribose nucleotides to the right side of the half circle 
representing the nucleus and turn RNA nucleotides right side up.

Attach the appropriate amino acid molecule to the appropriate tRNA 
molecule. 

Move the attached amino acid along with the tRNA to the appropriate 
bases on the RNA template.  Try to arrange these molecules so that 
they will be built on top of a circle used to represent a ribosome. 

Students will identify what amino acids they have put together by 
looking at a chart showing the codons used to represent various amino 
acids. 
                 
CONCLUSIONS: Each student has built a dipeptide made up of the amino 
acids leucine and serine.  Large protein molecules are built the same 
way, but with many more amino acids being brought to the mRNA template 
by tRNA. 

EVALUATION: Answer the following questions to show understanding of 
protein synthesis:

1. To join tRNA molecules to the mRNA pattern, which sequence of tRNA 
   molecules will match base pairs of the U,U,A sequence in mRNA?
2. Which tRNA sequence of bases can join U,C,A sequence in mRNA?
3. How does the sequence of bases on mRNA control the type of tRNA 
   joining it?
4. A base sequence of A,A,A mRNA could only join with what sequence of 
   bases in tRNA?
5. What specific amino acid is brought to the mRNA by a tRNA with a 
   terminal sequence of A,G,U? (Use an amino acid - codon table)
6. What amino acid is brought to the mRNA by a tRNA terminal sequence 
   of A,G,U?
7. How many half rungs of mRNA are responsible for the coding of one 
   amino acid?
8. A protein molecule consists of the following amino acid sequence: 
   leucine, glutamine, tyrosine, leucine, serine, serine.  What would 
   be the sequence of tRNA molecules responsible for forming this 
   protein? 
9. A ribosome receives the following mRNA message: AAA, CGA, GAA, GUU.   
   What will be the sequence of tRNA bases joining the mRNA molecule?
   B. What will be the sequence of amino acids formed from this code?
l0. Explain how a sequence of bases in DNA can instruct a cell to 
   produce a certain protein.