Pedigree Tutorial

What is penetrance?

• The probability of getting the condition given the mutation  

• Can be the probability of showing features at a certain age  

What is expressivity?

People that have the condition but have different presentations, features and severity  

What are the assumptions?

• Assumes that only one parent is a carrier  

• Not associated with a de novo mutation or low penetrance dominance  

What are the answers?

• ½ chance of Karim being a carrier  

• ½ x 1/20 x ¼ = 1/160 that baby is affected  

What is the equation for risk of affected offspring?

Chance of father being a carrier x chance of mother being a carrier x chance offspring is affected

What are the features of the Bayes theory?

• Combines risk information from different sources  

• Modifies the probability of an outcome based on conditional probabilities  

How does the Bayes work with CF has risk of 1/20 and negative carrier test that is 80% sensitivity?

What are the assumptions and mode of inheritance?

• Assumed to be autosomal dominant with reduced penetrance, could be X-linked or mitochondrial but less likely

• Assumes that Teagan has the same condition as the other family members  

• Assumes that it isn’t de novo  

• Assume that the mother is a carrier of the mutation