Final answer:
The codon that also encodes for phenylalanine, in addition to UUU, is UUC, and this redundancy reflects the nature of the genetic code.
Step-by-step explanation:
The codon for phenylalanine is UUU, and the codon that also most likely encodes for phenylalanine is UUC. This follows from the redundancy of the genetic code, wherein some amino acids are specified by more than one codon. It's important to note that certain codons like AUG have special functions, such as initiating protein synthesis, and are not the correct answer in this context. Moreover, triplets such as AAA and CCC encode for lysine and proline, respectively, not phenylalanine.