If the genetic code were read in groups of two bases, how many different codons would be possible? (Enter your answer as a numeral, not a word; e.g., enter 5, not "five.")

Question

Fill in the blank(s) with the appropriate word(s).

Answer 1

16

Clarify Question
• What is the key concept addressed by the question?
        o This question addresses the genetic code.
• What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.
• What key words does the question contain and what do they mean?
        o The genetic code is the set of codons that encode amino acids, by which mRNAs are read into proteins.
        o The codons are the (normally) three-base codes, such as ATG or CCG.

Gather Content
• What do you already know about the genetic code?
        o The genetic code is a set of 64 codons that encode amino acids using sets of three bases.
        o Since there are only twenty amino acids, the code is degenerate-there are multiple ways to encode each of the amino acids.

Consider Possibilities
• What other information is related to the question? Which information is most useful?
        o Consider the real genetic code. There are 64 codons.
        o There are four possible bases for spot 1, four possible bases for spot 2, and four possible bases for spot 3.
        o In total, that makes 4 × 4 × 4 possible combinations of bases.

Choose Answer
• Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o So for a 2-base genetic code, there would be four possible bases for spot 1, and four possible bases for spot 2.
        o In total, that makes 4 × 4 possible combinations of bases, or 16.

Reflect on Process
• Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray?
How can you revise your approach to produce a more desirable result?
        o This question asked how many codons would there be if it was a 2-base, not 3-base genetic code.
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that there would be four possibilities for each of the two bases?
        o Did you recognize that this problem requires the product rule, since each base is independent?
        o Do you see why nature uses a 3-base codon to encode the twenty amino acids, even though that creates "extra" degenerate codons?