Pedigree analysis problem with solution (example 13)
Q) The following pedigree shows the inheritance of ataxia, a rare neurological disorder characterized by uncoordinated movements. Is ataxia caused by a dominant or a recessive allele? Explain.
- The trait appears in every generation ( No skipping of generations)
- Nearly every affected individual has an affected parent.
The exception IV-2 individual had a father who carried the ataxia allele but did not manifest the trait. This shows incomplete penetrance.
A disease is said to show incomplete penetrance when some individuals express the associated trait while others do not even though they carry the disease causing gene.