Fig 1. Overview of chromosome-wide to gene-by-gene dosage alterations.

Artistic representation of the beneficial and the disadvantageous aspects of gene dosage alterations. Examples of naturally occurring and disease-causing phenomena are shown in the illustration. Such gene dosage alterations can occur from any level, from the chromosome-wide, i.e., mega-base scale, down to the individual gene level, i.e., a single-nucleotide change. Dosage can be modulated by genetic and epigenetic mechanisms.