An array, comprising: a support comprising a plurality of discrete wells; a gel material (24, 24') positioned in each of the plurality of discrete wells; and a quality control tracer comprising a cleavable nucleotide sequence comprising a cleavage site and a detectable fluorescent label; wherein the cleavable nucleotide sequence comprises a grafted region with a first end and a second end, where the first end is grafted to the gel material and the second end is linked to a cleavable region that is linked to the detectable fluorescent label and comprises the cleavage site; wherein the cleavable nucleotide sequence is grafted to the gel material at its 5' end and the detectable fluorescent label is attached at or near the 3' end of the cleavable nucleotide sequence; wherein said quality control tracer is grafted to the gel material in each of the plurality of discrete wells; and wherein either: (i) the portion of the cleavable nucleotide sequence which remains attached to the gel material after cleavage is a non-reactive nucleotide sequence, and thus will not actively participate in a particular DNA or RNA synthesis that is being performed or interfere with sequencing, and the quality control tracer is present in a predetermined ratio with an unlabeled primer nucleotide sequence (20, 20') grafted to the gel material in each of the plurality of discrete wells; or (ii) the portion of the cleavable nucleotide sequence which remains attached to the gel material after cleavage comprises a primer nucleic acid sequence. a support comprising a plurality of discrete wells; a gel material (24, 24') positioned in each of the plurality of discrete wells; and a quality control tracer comprising a cleavable nucleotide sequence comprising a cleavage site and a detectable fluorescent label; wherein the cleavable nucleotide sequence comprises a grafted region with a first end and a second end, where the first end is grafted to the gel material and the second end is linked to a cleavable region that is linked to the detectable fluorescent label and comprises the cleavage site; wherein the cleavable nucleotide sequence is grafted to the gel material at its 5' end and the detectable fluorescent label is attached at or near the 3' end of the cleavable nucleotide sequence; wherein said quality control tracer is grafted to the gel material in each of the plurality of discrete wells; and wherein either: (i) the portion of the cleavable nucleotide sequence which remains attached to the gel material after cleavage is a non-reactive nucleotide sequence, and thus will not actively participate in a particular DNA or RNA synthesis that is being performed or interfere with sequencing, and the quality control tracer is present in a predetermined ratio with an unlabeled primer nucleotide sequence (20, 20') grafted to the gel material in each of the plurality of discrete wells; or (ii) the portion of the cleavable nucleotide sequence which remains attached to the gel material after cleavage comprises a primer nucleic acid sequence. (i) the portion of the cleavable nucleotide sequence which remains attached to the gel material after cleavage is a non-reactive nucleotide sequence, and thus will not actively participate in a particular DNA or RNA synthesis that is being performed or interfere with sequencing, and the quality control tracer is present in a predetermined ratio with an unlabeled primer nucleotide sequence (20, 20') grafted to the gel material in each of the plurality of discrete wells; or (ii) the portion of the cleavable nucleotide sequence which remains attached to the gel material after cleavage comprises a primer nucleic acid sequence.