Microdeletion

Microdeletion: The loss of a tiny piece of a chromosome, a piece so small its absence is not apparent on ordinary examination (using a regular light microscope to look at chromosomes prepared in the usual fashion). The detection of microdeletions requires special techniques such as high-resolution chromosome banding, molecular chromosome analysis (with FISH), or DNA analysis.

Disorders caused by microdeletions include the Angelman, DiGeorge, Prader-Willi, and Williams syndromes.

The prefix "micro-" is derived from the Greek "mikros" meaning small. It diminishes whatever it precedes.