Penetrance and expressivity Flashcards
Not all patients with the same gene mutation (i.e. genotype) exhibit the same degree of observable characteristics (i.e. phenotype). TRUE/FALSE
TRUE
The proportion of a population of individuals who carry a disease-causing allele who express the related disease phenotype.
i.e. describes ‘how likely’ it is that a condition will develop
Penetrance
The extent to which a genotype shows its phenotypic expression in an individual.
i.e. describes the ‘severity’ of the phenotype
Expressivity
What factors can affect penetrance and expressivity
Modifier genes
Environmental factors
Allelic variation
Give examples of conditions with incomplete penetrance
retinoblastoma and Huntington’s disease
Give an example of a condition which has 100% or complete penetrance
achondroplasia
give an example of a condition with a high level of expressivity
neurofibromatosis