What is the chance that Jenny has inherited Tourette syndrome? Which phenomena that affect Mendelian ratios are exhibited by Tourette syndrome?
The correct answer and explanation is:
Tourette syndrome is a neurodevelopmental disorder characterized by involuntary movements and vocalizations, known as tics. The inheritance of Tourette syndrome follows a complex genetic pattern, but it is often considered an autosomal dominant condition. This means that a single copy of the mutated gene is sufficient to express the condition. If Jenny has a parent with Tourette syndrome, she has a 50% chance of inheriting the disorder, assuming the parent’s condition is due to a single dominant allele.
However, the inheritance of Tourette syndrome does not follow a simple Mendelian pattern in all cases. While the genetic risk is elevated in individuals with a family history of the disorder, many cases appear to be sporadic, meaning they arise in individuals with no prior family history. This suggests that multiple genes, and possibly environmental factors, contribute to the disorder.
Phenomena that affect Mendelian ratios and are exhibited by Tourette syndrome include incomplete penetrance and variable expressivity. Incomplete penetrance occurs when an individual inherits a dominant allele for a disorder but does not express the condition. In the case of Tourette syndrome, a person may carry the genetic mutation but not show symptoms. Variable expressivity refers to the differences in the severity and type of symptoms among individuals who have inherited the same genetic mutation. In Tourette syndrome, some people may have mild symptoms, while others may experience more severe tics that interfere with daily life.
The genetic complexity of Tourette syndrome challenges the classic Mendelian inheritance model, as environmental factors, gene interactions, and random genetic mutations can also play significant roles in the expression of the disorder.