Sequence encoding a linker and the Dendra2 photoconvertible fluorescent protein has been inserted into the endogenous His3.3A locus, at the C-terminal end of the open reading frame. In addition, four amino acid replacements have been introduced into the His3.3A coding sequence, changing the amino acids to those found in the His3 coding sequence in each case such that the final sequence is identical to that of wild-type His3.