Modeling discordance in identical twins

Background: identical twins aren’t

It is not uncommon for a genetic condition to show unexplained heterogeneity, that is, the same variant produces different effects in isogenic individuals. A striking example comes from neurofibromatosis type 1, a monogenic condition. Adam and Neil Pearson both carry the same variant in the NF1 gene, but while Neil’s symptoms are invisible, Neil’s are very nearly the opposite.

Here we will look at a larger cohort of identical (monozygotic) twins to study discordant phenotypes such as weight and muscle mass using mixture models. The

The preceding data is from monozygotic (identical) twins of varying age. We can get an idea of how long the twins have had to diverge based on how old they were when the measurements were taken.

It doesn’t look like there is any age dependence in terms of phenotypic drift.