Aminoallyl-dUTP-X-Cy3 is a fluorescently labeled nucleotide analog structurally related to natural dTTP. It is incorporated enzymatically into DNA sequences using standard methods such as PCR amplification, reverse transcription, nick translation, or random priming reactions. Upon incorporation, it imparts red fluorescence (excitation/emission: 550/570 nm) to synthesized DNA strands. This fluorescent labeling enables visualization and detection in molecular biology assays, including in situ hybridization, blot hybridization techniques, multi-color fluorescence microscopy, and DNA microarray analyses.