Based on the results obtained by analyzing the polypeptides produced by the three artificial mRNA strands, the best conclusion to make is that the genetic code is degenerate.
Degeneracy in the genetic code means that multiple codons can code for the same amino acid. In this case, we can observe that different mRNA strands (x, y, and z) produce different polypeptides, but these polypeptides have the same amino acid composition.
Let's break it down:
1. Strand x produces a polypeptide that is 50% phenylalanine and 50% lysine.
2. Strand y produces a polypeptide that is 50% phenylalanine and 50% proline.
3. Strand z produces a polypeptide that is 50% isoleucine and 50% tyrosine.
From these results, we can see that different mRNA sequences (x, y, and z) can produce polypeptides with the same amino acid composition, indicating that the genetic code is degenerate.
This degeneracy is due to the presence of multiple codons that can specify the same amino acid. For example, phenylalanine can be coded by the codons UUU or UUC, and lysine can be coded by the codons AAA or AAG. Similarly, proline can be coded by the codons CCC, CCA, CCG, or CCU, and isoleucine can be coded by the codons AUU, AUC, or AUA.
In summary, the results suggest that the genetic code is degenerate, meaning that multiple codons can code for the same amino acid. This provides flexibility and redundancy in the translation process, allowing for error correction and adaptation to different conditions.