UGAKodons

UGAKodons is a term sometimes used in biology education and literature to refer to the UGA triplet in messenger RNA, which functions as a signal during translation. In the standard genetic code, UGA, along with UAA and UAG, acts as a stop codon that terminates polypeptide synthesis.

In certain cellular contexts, UGA can be recoded to incorporate the amino acid selenocysteine, producing functional proteins that require selenium. This recoding demands a selenocysteine insertion sequence (SECIS) element in the mRNA and specialized translation factors. As a result, UGA can be read either as a stop signal or as a codon for selenocysteine, depending on context.

UGAKodons thus exemplify genetic code flexibility and translational regulation. Their interpretation depends on the organism, the mRNA structure, and the presence of SECIS elements and tRNA^Sec. In most standard annotations, UGA is treated as a termination signal, but in selenoprotein genes it is decoded as selenocysteine.

This concept highlights key themes in molecular biology, including codon usage, the mechanics of translation termination, and the special cases that expand the functional diversity of the genetic code. See also genetic code, UGA codon, selenocysteine, and translation termination.