DNA molecules consist of chemically linked sequences of the bases adenine, quinine, cytosine, and thymine, denoted A, G, C, and T. A sequence of 3 bases is called a codon. A base may appear more than once in a codon.
The bases A and G are purines, while C and T are pyrimidines.
How many codons are there whose first base is a purine and the second and third bases are pyrimidines?
I know the answer is 8, but why is it 8? Why is it 2^3?
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you might get a better response if you post in Biology. if this is an application probability then|dw:1443893477530:dw|
there are 2 sets that we can divide this into to start with; those that start with A, and those that start with G
each set can be divided into subsets; those that follow with a C, and those that follow with a T; so we are up to 2 sets, that have 2 elements each. 4 in total
these 4 elements, can either end with a C or a T, so each one can be finished in 2 ways ... 4*2 = 8