Abstract: The present application provides a reusable microarray comprising a plurality of immobilized oligonucleotide probes each having one or more nucleotides that are resistant to cleavage. The microarray is useful for analyzing nucleic acids, including single nucleotide polymorphisms (SNPs) by extension or ligation assays. The microarray can be reused by treatment that cleaves non-resistant extension or ligation products on the free termini of the oligonucleotide probes.