Abstract: Techniques for producing cloned DNA sequences are provided which sequences are complementary to DNA occurring in one selected region of one chromosome of a multi-chromosomal genome, such as the human genome. Such cloned DNA sequences can be labeled and formed into probes by conventional procedures, there are provided methods for making probe compositions which comprise mixed DNA segments derived from such a DNA sequence. An improved DNA sequence transamination procedure is provided utilizing trifluoroacetate chaotrope anions. With high concentrations of low complexity DNA, high levels of transamination are thereby achieved. These segments are covalently bound to fluorophore groups through linking groups that are transaminated preferably chaotropically into the segments.