Affymetrix (GeneChip Human Genome U133 Plus 2.0 Array) Probesets Mapping and
Annotations Database (APMA)
One of the key problem facing microarray experiments is insufficient reliability of expression measurements due
to sub-optimal probe design. APMA classifies GeneChip Human Genome initial target sequences based on specificity,
complexity, and reliability to use in gene expression measurements. Discrepancies found in probeset annotation and
target sequence mapping account for up to 30% of probesets, including about 25% of Affymetrix probesets derived from
target sequences overlapped interspersed repeats and 1.8% of original target sequences with erroneous orientation of
the sequences. 86% of U133 target sequences passed APMA software quality-control filtering. APMA provide design and
visualization pipelines and DB for quality control of the initial probe sequences and analysis of U133 Plus 2
microarray measurements but can have general applicability to a variety of human gene expression profiling projects.