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The situation in which an individual who is heterozygous for a certain gene mutation or hemizygous at a particular locus, often due to a deletion of the corresponding allele, is clinically affected because a single copy of the normal gene is incapable of providing sufficient protein production as to assure normal function

Definition from: GeneReviewsThis link leads to a site outside Genetics Home Reference. from the University of Washington and the National Center for Biotechnology Information

See also Understanding Medical Terminology.

Published: February 8, 2016