Consider a protein composed of only 21 amino acids encoded by a short ORF that is located between two known genes in a mammalian genome. Due to its...

Consider a protein composed of only 21 amino acids encoded by a short ORF that is located between two known genes in a mammalian genome. Due to its length, the ORF had not been annotated as a gene. What methods can demonstrate that it is indeed a gene that is actively translated to protein and why?