X-linked

X-linked dominant inheritance

X-linked dominant inheritance is the pattern by which a trait encoded by an allele on the X-chromosome is passed down through generations, wherefore only one copy of that allele is sufficient for an individual to be affected (dominance). Unlike with X-linked recessive traits, females are more often affected by X-linked dominant traits than males as females have two X-chromosomes as opposed to one. Moreover, some X-linked dominant conditions (for example, Aicardi syndrome) are embryonically or neonatally lethal in hemizygous males (XY), and thus can be seen to only affect heterozygous females, who experience less severe symptoms.