A cataract is clouding of the crystalline lens of the eye and has a genetic component in its cause.
It is inherited as an autosomal dominant mutation; about 50% of the offspring of a heterozygous individual
are expected to show the trait.
This pedigree is consistent with an autosomal dominant mode of inheritance, but does not prove it.
The presence of an unaffected daughter in generation IV argues against X-linkage,
since she received her X chromosome from her affected father.
