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A phenotype that requires only one copy of the causal variant in an individual for the phenotype to occur.

Use in clinical context

Individuals have two copies of each gene, with the exception of genes on the sex chromosomes in males, and both copies can contribute to an individual’s phenotype. When a dominant variant is present it is expressed irrespective of the other copy of the gene. Dominant variants can still be influenced by other factors which can result in the phenotype not being expressed or different forms of presentation, despite the presence of the dominant variant or gene.

Last updated on 3rd June, 2019