How many possible trinucleotides are there that contain all three of the following bases: adenine (A),cytosine (C),guanine (G)?

Question

Quizplus · Accepted Answer

There are 3 possible positions for each base, so the total number of trinucleotides is 3 x 3 x 3 = 27. However, if we only want the trinucleotides that contain all three bases, then we need to subtract the ones that only have two of the three bases. There are three such trinucleotides (AAC, CGC, and GAG) because each base can be in either the first, the second, or the third position. Therefore, the total number of trinucleotides that contain all three bases is 27 - 3 = 24. However, since each trinucleotide can be read forwards or backwards, there are really only 12 unique trinucleotides that contain all three bases. Finally, since the question is asking for the number of trinucleotides and not the number of distinct trinucleotides, the answer is 6.

How Many Possible Trinucleotides Are There That Contain All Three