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The CENTRAL DOGMA
Make a Protein – Transcription and Translation
DNA  RNA  Protein
The four nitrogenous bases in DNA (A,C, G and T) create a
code. Cells “read” this DNA code to make proteins, the building
blocks of all organisms.
This is done in two steps:
1. Copying the DNA sequence– Transcription
2. Reading the copy to string together the small molecules
(amino acids) that make up a polypeptide - Translation
Reading a Copy of DNA instructions to Assemble a Polypeptide - Translation
Cells read DNA in small portions (genes) to create a protein. To do this, the cell must first make a
copy of the gene’s code to send to the protein-building organelle, the ribosome. This process is
called transcription. This copy, mRNA, is a recipe for assembling a polypeptide. Polypeptides are
built from small molecules (monomers) called amino acids. The mRNA travels from the nucleus to
the ribosome and the appropriate amino acids are assembled into a polypeptide chain – the primary
structure of a protein. This process is called Translation.
Work with the group at your table for this task. Use the key below and simulate Transcription.
You will need:
o Previously made model of mRNA
o Rectangle cut outs
o Tape
o Colored pencils
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Procedure:
1. Begin to create your polypeptide. At your table, join all of your mRNA to make a long
mRNA strand. (27 bases long if there are 3 in your group, 18 bases long if there are 2 in your
group.) In your notebook, record the bases that are present in your new, long strand of
mRNA.
2. Assemble a start and a stop codon. Each group of two must complete this step! At the
beginning and the end of your new, long strand of mRNA, attach a start and a stop codon. To
do that:
 cut out and label a rectangle to represent a start codon and a rectangle to represent a
stop codon
 Place them at the beginning and end of your long strand.
3. Use your new model of mRNA (created in Step 1) and the amino acid rectangle cut-outs to
create a polypeptide chain. To do this:
 cut out a rectangle and label it with the correct amino acid that is coded for by the first
codon from your mRNA molecule.
 Repeat this process for the remaining codons in your mRNA molecule.
 Color each amino acid a unique color. For example, color all the lysine red, all the alanine
blue.
4. Bond your polypeptide. Tape your amino acids together in the correct order as coded for in
your mRNA strand. Don’t forget to bond your start and stop codons at the beginning and the
end of your new, polypeptide. Tape the polypeptide into your notebook.
5. Get your polypeptide checked. Get a stamp in your composition book.
Analysis: (Answer these in your composition book):
1. Take your model of mRNA and delete the 5th base, how does the resulting amino acid
sequence change? Draw the new polypeptide from this change.
2. Take your model of mRNA and delete the 3rd codon, how does the resulting amino acid
sequence change? Draw the new polypeptide from this change.
3. Take your model of mRNA and substitute the 5th base with a different base, how does the
resulting amino acid sequence change? Draw the new polypeptide from this change.
4. Give an example of one other alteration in your mRNA that will affect the final amino acid
sequence.
5. Some changes have no effect on the final amino acid sequence. Give an example.
Conclusion: (Answer these in your composition book)
1. What enzyme adds nitrogenous bases to mRNA?
2. In what part of the cell does transcription take place?
3. In your own words, describe transcription.
4. What is the protein-building organelle?
5. What kind of RNA brings the amino acid to the ribosome?
6. What kind of RNA contains the anticodon?
7. In what part of the cell does translation take place?
8. In your own words, describe translation.
9. What does the tape on your amino acid sequence represent?
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