TRANSCRIPTION AND TRANSLATION

How does the sequence of bases in DNA determine the order of bases in mRNA?
How does the sequence of bases in mRNA determine the order of amino acids in a protein?

Colored pencils/crayons
DNA nucleotide models (6 of each, total of 24)
RNA nucleotide models (3 of each, total of 12)
Clear tape

   1. Color the DNA nucleotide models. Use a different color of the each of the four bases. For example,
       color all the adenines red, the cytosines blue, the guanines yellow, and the thymines green. COLOR
   2. Cut out each DNA nucleotide.
   3. Use the 24 DNA nucleotides to construct a double-stranded DNA molecule. The first the 3 bases of the
       upper strand should be TAC and the last 3 bases should be ACT. In between, you may use any sequence
       of bases that you choose.
       Remember, the sequence of bases on the lower strand must be complementary to the bases of the upper
   4. Fasten the molecule together using clear tape to connect the nucleotides of each strand. Do not tape
       across base pairs.
   5. Write the sequence of DNA bases below.
       Upper: ___________________________________________________________
       Lower: ___________________________________________________________
   6. Now color the RNA nucleotide models. Use the same three colors you used before for the As, Cs, and
       Gs. Use a different color for the Us. AGAIN, COLOR ONLY THE BASES.
   7. Cut out each RNA nucleotide.
   8. Separate the upper and lower strands of DNA.
   9. Using the upper strand of DNA, match complementary RNA nucleotides with the exposed bases of the
       DNA strand to make an mRNA molecule.
   10. When you are finished, tape the mRNA molecule together.
       Write the sequence of RNA bases below:
   11. Now, use the codon chart on p. 292 of your textbook to determine the sequence of amino acids encoded
       by the mRNA. Fill in the amino acid sequence below.

Questions (answer on the back of this sheet)
  1. Does the mRNA strand more closely resemble the DNA strand from which it was transcribed or the
      complementary DNA strand that wasn’t used? Explain.

   2. In which step of the procedure did you simulate transcription? _____

   3. In which step did you simulate translation? _____

   4. Which would be more damaging to a cell, an error in DNA replication or transcription? Explain.

   5. With regard to transcription and translation, describe how a change in the sequence of DNA bases in a
      gene (a mutation) could lead to a change in the functioning of a protein.

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