fixed human metaphase chromosomes , whose dna had been substituted with 5'-bromodeoxyuridine ( brdurd ) for two rounds of replication ( tb/bb ) or for one round in brdurd followed by another round in thymidine ( tt/bt ) , were treated with ultraviolet light ( uv ) , in the presence or in the absence of 33258 hoechst , to produce sister chromatid differentiation ( scd ) .
C0012854
dna
C0598312
replication