What are stop codes in genetics?

Stop codes, or stop codons, in genetics are specific sequences of nucleotides in messenger RNA (mRNA) that signal the termination of protein synthesis. When the ribosome encounters a stop codon during translation, it recognizes that the polypeptide chain is complete, and the process of building a protein is halted. This ensures that proteins are synthesized to their appropriate lengths, as dictated by the genetic code.

The stop codons commonly referred to are UAA, UAG, and UGA. These do not code for any amino acid but rather prompt the release factors to bind to the ribosome. This triggers the disassembly of the translation machinery and the release of the newly synthesized polypeptide.

In contrast, other choices refer to different aspects of genetic processes. The signals for DNA replication involve sequences that initiate the unwinding of DNA, markers for transcription initiation are sites where RNA polymerase binds to start transcription, and region codes for genetic mutations pertain to variations in DNA sequences that can affect protein function or expression. None of these relate directly to the halt of protein synthesis, which is exclusively the role of stop codes.