Compositions and methods for evaluating genomic alterations

A plurality of target capture reagents, comprising first target capture reagents (R1s), wherein each R1 comprises an oligonucleotide comprising a first nucleic acid sequence that hybridizes to a first target nucleic acid sequence, wherein the oligonucleotides of the R1s are the same, and second target capture reagents (R2s), wherein each R2 comprises an oligonucleotide comprising a second nucleic acid sequence that hybridizes to a second target nucleic acid sequence, wherein the oligonucleotides of the R2s are the same, wherein:

• a first portion of the R1s comprises a first member of a binding pair;
• a second portion of the R1s lacks the first member of the binding pair;
• a first portion of the R2s comprises the first member of the binding pair;
• and
• a second portion of the R2s lacks the first member of the binding pair;
• wherein the first member of the binding pair binds a second member of the binding pair disposed on a substrate, and
• wherein the proportion of R1s that comprises the first member of the binding pair is greater than the proportion of R2s that comprise the first member of the binding pair.