Final answer:
A nonsense or frameshift mutation could lead to the bacteria not glowing, as both can result in non-functional proteins that disrupt the bioluminescence pathway. Silent mutations are less likely to cause this effect, while missense mutations may or may not, depending on their location within the protein sequence.
Step-by-step explanation:
The bacteria not glowing in response to added signal molecules could be due to a mutation affecting the genes responsible for the bioluminescence pathway.
Among the options provided, a nonsense mutation and a frameshift mutation are most likely to cause the bacteria to lose its ability to glow.
A nonsense mutation could introduce a premature stop codon, which would truncate the protein and likely disrupt its function.
Similarly, a frameshift mutation, caused by the insertion or deletion of a nucleotide, can alter the reading frame of the gene, leading to a completely different amino acid sequence downstream from the mutation, and likely resulting in a non-functional protein.
In contrast, a silent mutation does not change the amino acid sequence of a protein, so it is less likely to be responsible for the loss of glow.
A missense mutation, which substitutes one amino acid for another, could potentially disrupt protein function, but its effect would be more localized to the mutation site and might not completely abolish the protein's function, unless it occurs at a critical site for protein activity.