Chromosome Resolution Additive (CRA) is a newly discovered commercial formulation that consistently prevents chromosome contraction and encourages chromosome elongation by loosening the chemical bonding within the supercoiled structure of the chromosome. The result is prophase quality chromosomes. It was developed especially for tissues resistant to existing prophase techniques, such as bone marrows and solid tumors. CRA contains no ethidium bromide or thymidine.

Exposure of any cell cultures to colchicine induces super contracted chromosomes. The presence of CRA greatly antagonizes the super-contraction induced by colchicine, by interfering with the molecular bonding of the chromosome contraction process. In other words, it acts like a molecule “wedge” causing the chromosome structure to elongate.