Over the last few decades, techniques in the field of cytogenetics have greatly improved, which has led to a significant increase in the detection rate of chromosomal aberrations. In traditional cytogenetic techniques, the resolution level is limited to at best ≈5 Megabases (Mb), and smaller chromosomal aberrations are generally not detected. In order to solve this problem and achieve a higher resolution, metaphase chromosomes have been replaced by oligonucleotide arrays, which provide a resolution as fine as just a few Kilobases (Kb). These new technologies are summarized under the terms "Molecular Karyotyping" and "Array Comparative Genomic Hybridization (Array CGH)".
Affymetrix´ and Agilent´s microarray platforms are among the world’s leading DNA chip technologies. Agilent’s CGH arrays provide a powerful tool for the genome-wide detection of copy number variations (CNVs). Affymetrix´ Human SNP Array 6.0 and the CytoScan HD Array can be used for SNP Genotyping and for the detection of genetic imbalances, such as copy number variants (CNVs), loss-of-heterozygosity (LOH), and copy number-neutral LOH (uniparental disomy).