The invention relates generally to the field of the identification of DNA sequences, genes or chromosomes. Methods and composition to obtain Unique Sequence DNA probes are provided. Compositions comprises of and double stranded DNA containing Unique Sequences from which the repetitive sequences are eliminated according to the method described in this invention. The invention also relates to the preservation of cells that have been identified after immunomagnetic selection and fluorescent labeling in order to further interrogate the cells of interest. Furthermore the invention relates to genetic analysis of cells that have been identified after immunomagnetic selection and fluorescent labeling.