The segment of an mRNA molecule from its 5′ end to the start codon of the structural gene. The leader contains ribosome-binding sites and facilitates the initiation of genetic translation. In eukaryotes, the leader sequence is not usually translated. In prokaryotes, the leader may contain an attenuator (q.v.) segment that is translated. The resulting peptide functions to terminate transcription before the RNA polymerase reaches the first structural gene of the operon. See exon, trailer sequence.
Subjects: Medicine and Health — Genetics and Genomics.