What is the role of the start codon in the coding sequence?

The start codon plays a crucial role in the initiation of translation, which is the process of synthesizing proteins from messenger RNA (mRNA). Specifically, the start codon, which is typically AUG, signals the ribosome to begin translating the mRNA into a polypeptide chain.

When the ribosome encounters the start codon, it recognizes that this is where translation should commence, and it ensures that methionine, which corresponds to that codon, is the first amino acid incorporated into the growing polypeptide chain. This is significant because the presence of methionine establishes the correct reading frame for the ribosome, allowing for accurate translation of the entire coding sequence.

The other choices mention processes related to translation and RNA processing but do not pertain directly to the function of the start codon in protein synthesis. For instance, ending translation is associated with stop codons, while tRNA does connect with codons, but the specific initiation codon’s primary role is to initiate the process and specify the first amino acid, methionine. The spliceosome's binding function pertains to RNA splicing, which is a different stage of gene expression that occurs in eukaryotes after transcription.