Say, in the context of finding microbial life on Mars (i.e., organisms that evolved from the start with six nucleotides, not just taking current terrestrial organisms and swapping out the nucleic acids and ribosomes).
Say, in the context of finding microbial life on Mars (i.e., organisms that evolved from the start with six nucleotides, not just taking current terrestrial organisms and swapping out the nucleic acids and ribosomes).
There are 4 × 4 × 4 = 64 possible codons, but only 20(-ish) amino acids. This leaves quite a few spares for some built-in redundancy.
For example, UCU, UCC, UCA, and UCG all code for Serine. The third letter can mutate or be mistranscribed, and still produce an identical protein.