An assembly and a method are disclosed for analyzing nucleic acid sequences by way of so-called sequencing-by-synthesis. According to an embodiment of the invention, a chemical substance group that is released when a nucleotide bonds to a nucleic acid sequence to be sequenced is detected. The reagents are applied by way of a spraying device to a sensor that detects the released substance group. This has the advantage that no lateral flow occurs. The rate of false-negative and false-positive results is significantly reduced. Furthermore, a small amount of the reagent is sufficient to completely wet the sensor. Filling of the supply and discharge lines as for a flow cell is not necessary.