Question

A non-sense mutation results into

• A. Stoppage of transcription
• B. Change in protein structure
• C. Stoppage of protein synthesis
• D. Termination of polypeptide chain

Answer 1

Answer: (D)

Termination of polypeptide chain

Transcription termination is independent on presence or absence or stop codon; it occurs by $\rho$-independent and $\rho$-dependent mechanism. A nonsense mutation is a kind of point mutation in DNA. It results in the introduction of the premature stop codon, or a nonsense codon in the transcribed mRNA thereby causing the termination of that polypeptide chain. Premature termination of translation causes shortening of polypeptide chain; it does not change the amino acid sequence and hence, no effect on its primary or secondary structure. The introduction of stop codon terminate synthesis of that particular gene; it does not cause stoppage of protein synthesis and the process is carried out till RNA polymerase encounter the stop codon. Thus, the correct answer is option D.