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This activity is designed to help students understand how the genetic code works for amino acids. Please answer the following questions in your activity journal page.

Access the Student Journal for Activity 1

Activity 1 - Information Coding

This activity is designed to help you understand how the genetic code allows many different types of amino acids to be created. Complete the activity on your student journal sheet.

1. Calculate the following:

a. How many amino acids could be coded for if there were only four nucleotides operating singly?
b. How many amino acids could be coded for if the nucleotides occurred in the pairs shown below? That is, how may different ways can you write a string of letters A-A, A-T, A-C, etc.?


c. Can you state the number of possibilities by a mathematical expression?

2. Clearly, four pairs cannot specify 20 amino acids. What mechanism do you suppose cells have for specifying the large number of amino acids?

If an amino acid could be specified by two nucleotide pairs, it would not be possible to specify 20 amino acids. But suppose it took a sequence of THREE nucleotides to specify any given amino acid. Then, the total possibilities, 43 = 64, is more than enough to code for 20 amino acids. Clever experiments some 35 years ago revealed that this is the coding scheme used by cells. The complete code for amino acids seems to be as shown in activity 2.

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