DNA molecules consist of chemically linked sequences of the

DNA molecules consist of chemically linked sequences of the bases adenine, guanine, cytosine and thymine, denoted A, G, C and T. A sequence of three bases is called a codon. A base may appear more than once in a codon.

1) Represent all possible base sequences using a tree diagram.

2) How many different codons are there?

3) The bases A and G are purines, while C and T are pyrimidines. How many codons are there whose first and third bases are purines and whose second base is a pyrimidine?

4) How many codons consist of three different bases?

Solution