text: The goal of combining fluorescence and nucleic acids has been to provide a non-isotopic tag that is detectable to study DNA or RNA. This type of labeling allows scientists to study DNA or RNA in their structure, function, or formation with other nucleic acids. The first base modification for fluorescent labeling occurred in 1971 with a 4-thiouridine and 4-thiouracil. This research along with others, which included various types of direct and non-direct labeling via: analogs, addition via enzymes, or other methods made labeling of nucleotides much safer for scientist to study DNA.
  As instrumentation and technologies become more advanced in the field of DNA microarray, better reagents and techniques will be needed to further scientific studies. Fluorescent labeling with Cy3 was shown to be more insufficient and skew results; the method of aminoallyl nucleotide incorporation was opted instead. Using aminoallyl nucleotides as indirect fluorescent labeling seemed to nullify the sensitivity issues seen in cyanine-labeling.