Why is the position of the first AUG after the ribosome binding site critical?
A) Every polypeptide must start with methionine.
B) It initiates transcription.
C) Every polypeptide must start with arginine.
D) It establishes the reading frame.
E) Every polypeptide must end with methionine.

Question

Quizplus · Accepted Answer

The position of the first AUG after the ribosome binding site is critical because it establishes the reading frame. The ribosome reads the mRNA in groups of three nucleotides, called codons, and starting at the wrong codon can shift the reading frame and produce an incorrect amino acid sequence for the polypeptide. Methionine is typically the first amino acid incorporated into a protein, but not all polypeptides start with methionine, so option A and E are incorrect. Option B is incorrect because AUG initiates translation, not transcription. Option C is incorrect because not all polypeptides start with arginine.

Why Is the Position of the First AUG After the Ribosome