Selenocysteine is 21st AA coded by UGA which is normally a stop codon. Pyrrolysine is 22nd AA coded by UGA which is also a stop codon normally. Lysine is also an essential amino acid so has to be coded by codon (AAA, AAG). Hydroxyproline and hydroxylysine are not coded by a codon, i.e. they are not incorporated into protein during translation. Rather, they are formed in protein, by post-translational modification (hydroxylation) of proline and lysine, respectively. "Ornithine is not an amino acid coded for by DNA, and, in that sense, is not involved in protein synthesis.