Practice question

Comparative Genomic Hybridization was developed to survey genome-wide copy number alterations in tumor samples where karyotyping is challenging. By competitively hybridizing fluorescently labeled tumor DNA and normal reference DNA to normal metaphase chromosomes or microarray probes, gains and losses are visualized as altered green-to-red ratios. Amplifications of oncogenes and deletions of tumor suppressor loci are revealed across chromosomes. CAGE maps TSS, DNA microarrays measure expression, and run-off assays measure transcription rates, none providing direct genome-wide copy number and structural aberration assessment inherent to CGH design.