If a codon in the Rdl GABA receptor cDNA is replaced with an amber codon, what is the outcome for receptor synthesis?

• A. The receptor will be synthesized normally
• B. Receptors will accumulate in the Golgi complex
• C. The receptor cannot be synthesized
• D. Receptors will be expressed in the cytosol

Answer: (C)

Replacing a codon with an amber codon introduces a stop signal in the mRNA sequence. The amber codon, which is one of the three stop codons in the genetic code (UAG), signals termination of translation during protein synthesis. As a result, when a ribosome encounters an amber codon, it will stop protein synthesis prematurely.

In the context of the Rdl GABA receptor, if a codon that is crucial for its proper synthesis is replaced with an amber codon, the ribosome will terminate translation at that point. This leads to an incomplete protein that cannot fold properly or perform its necessary functions, ultimately leading to the conclusion that the receptor cannot be synthesized at all.

While the other choices reflect potential outcomes related to protein production and processing, they do not account for the fundamental impact of a premature stop codon, which unequivocally halts the translation process. Therefore, the process of receptor synthesis is effectively disrupted, confirming that the receptor cannot be synthesized.