This invention contemplates an accurate and efficient estimation of gene copy number using oligonucleotide microarrays. The method integrates gene copy number data obtained from perfect match and mismatch probe sequence structure intensities and probe binding affinities. In one embodiment, an accurate determination of single nucleotide polymorphisms (SNPs) sequences is obtained. In another embodiment, an accurate detection and determination of DNA copy number alteration is obtained. In another embodiment, an accurate estimation for RNA gene expression is obtained.