A term used to characterize heterozygous females that behave phenotypically as if they were carrying an X-linked recessive in the hemizygous condition. An example would be a hemophilic mother that has produced nonhemophilic sons. It is assumed, according to the Lyon hypothesis, that occasionally a particular tissue comes to be made up entirely of cells that contain inactivated X chromosomes carrying the normal allele. The phenotype of such a female heterozygote would then resemble that of mutant males. See manifesting heterozygote.
Subjects: Genetics and Genomics.