Wild-type His1 gene in the context of a histone gene repeat unit.
Mutated His3 gene in the context of a histone gene repeat unit; contains a K4A amino acid replacement.
Wild-type His2A gene in the context of a histone gene repeat unit.
Wild-type His2B gene in the context of a histone gene repeat unit.
Wild-type His4 gene in the context of a histone gene repeat unit.
Each copy of His3 has been mutated to contain the amino acid replacement K4A.
Clones triply homozygous for His3.3AKO, His3.3BKO and Df(2L)BSC104 survive if they are carrying both His3.3BK4A and two copies of M{3xHisGU.H3.2.K4A}, although the clones are smaller than their wild-type twin spots.