Which statement correctly describes stop codons?

Which statement correctly describes stop codons?

• A. They code for amino acids
• B. They signal termination
• C. They bind to E site
• D. They determine start codon

Answer: (B)

Stop codons signal termination of translation. In the genetic code, most codons specify a particular amino acid, but the stop codons—UAA, UAG, and UGA—do not encode any amino acid. When a ribosome encounters one of these at the A site, release factors bind and promote release of the finished polypeptide from the tRNA in the P site, effectively ending protein synthesis. Afterward, the ribosome subunits disassemble. They aren’t involved in binding at the E site, and they don’t determine the start of translation—that role belongs to the start codon AUG, which sets the reading frame and initiates synthesis.

Stop codons signal termination of translation. In the genetic code, most codons specify a particular amino acid, but the stop codons—UAA, UAG, and UGA—do not encode any amino acid. When a ribosome encounters one of these at the A site, release factors bind and promote release of the finished polypeptide from the tRNA in the P site, effectively ending protein synthesis. Afterward, the ribosome subunits disassemble. They aren’t involved in binding at the E site, and they don’t determine the start of translation—that role belongs to the start codon AUG, which sets the reading frame and initiates synthesis.