I believe the answer is A.
Because if the engineers are mixing genetics<span> around and making them not natural,</span>natural selection<span> won't work because the natural things won't be evolving in the natural way. </span>
The end of the protein-coding message is signaled by the presence of one of three codons (UAA, UAG, or UGA) called stop codons (see Figure 6-50). These are not recognized by a tRNA and do not specify an amino acid, but instead signal to the ribosome to stop translation.
