Cationic trypsinogen is an enzyme made in the pancreas that

Cationic trypsinogen is an enzyme made in the pancreas that helps to digest food. It is encoded for by the PRSS1 gene. Individuals with a disorder called hereditary pancreatitis have mutations in the PRSS1 gene, which result in inflammation of the pancreas, possibly leading to permanent tissue damage. The disorder is inherited in an autosomal dominant fashion. Imagine that you are part of a research team interested in determining the penetrance of a different PRSS1 mutation, Ala16Val. Your team has identified 120 individuals with the PRSS1 Ala 16Val allele and found that 48 of the individuals did not display any evidence of pancreatitis. From your data, what is the penetrance of the PRSS1 Ala16Val mutation? Express your answer as a whole number. If a man who is heterozygous for a PRSS1 Ala 16Val mutation mates with a woman who is homozygous for normal cationic trypsinogen, what is the probabilityy that their offspring will have hereditary pancreatitis, given the penetrance value obtained in Part B? Express your answer as a whole number.

Solution

Not all the traits are expressed 100% of time even though the allele is present. Penetrance is the frequency of expression of an allele when it is present in the genotype of the organism. If 5 out of 10 individuals carrying an allele express the trait, the trait is said to be 50% penetrant.

Part B: Out 120 individuals with PRSS1 Ala15Val allele and 48 did not display the phenotype, which means the rest of 72 individuals displayed the phenotype. So the penetrance for this gene would be 72/120, which is around 60%.

Part C: The probability would be 1 in 4 children born will have hereditary pancreatitis, so the penetrance would be only 25%.