gene imprinting

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gene imprinting The differential expression of a single gene according to its parental origin. For example, the symptoms of Huntington's disease, an inherited neuromuscular disorder caused by a dominant mutant allele, first occur during adolescence if the mutant allele is inherited from the male parent but symptoms generally do not arise until middle age if the allele derives from the female parent. At least some instances of gene imprinting are thought to be associated with the attachment of methyl groups to certain cytosine residues in the DNA of one parent.