When it comes to understanding how genetic conditions are passed from one generation to the next, the concept of ‘inheritance patterns is’ key. These patterns help families understand the likelihood of inheriting a particular genetic mutation or disease. An autosomal dominant inheritance pattern is what is present for families that carry genetic mutations that cause familial Alzheimer’s disease (FAD).
The basics of gene inheritance
Each person usually has two copies of every gene, with one copy coming from each parent. For some genetic diseases like FAD, inheriting just one mutated copy of a gene from one parent is enough to cause the disease. This scenario is what we call autosomal dominant inheritance.
How autosomal dominant inheritance works
In autosomal dominant inheritance, a person who carries a mutated gene has a 50% chance of passing this mutated copy on to each of their children. This means that each child has an equal likelihood of inheriting the disease, irrespective of gender or whether their siblings have already inherited it or not.
Essentially, it’s like a genetic coin toss for each child, where each flip is independent of the others. In families with an autosomal dominant disease, it's common to see the disease affecting individuals across multiple generations.
A family tree illustrating what an autosomal dominant disorder inheritance pattern looks like in a family. In this scenario, the mother has a mutation (green check mark) that is then passed on to her two children, regardless of gender.
A closer look at familial Alzheimer’s genetics
FAD follows an autosomal dominant disease pattern. If a person inherits just one copy of an FAD-related genetic mutation (APP, PSEN1, or PSEN2), they are likely to develop FAD. Each child of a parent with a mutation in one of these genes, has a 50% chance of inheriting the mutated gene and thus the disease.
Each child’s risk is separate
With autosomal dominant inheritance, every child has an independent 50% risk of inheriting the mutated gene. This probability resets with each child, meaning the presence of a mutation in one sibling does not influence the chances of another sibling inheriting the same mutation. Each child's genetic inheritance is a separate roll of the dice, and the chances of inheriting the mutation are the same for each child.
Understanding autosomal dominant inheritance can be crucial for families with a history of genetic diseases, as it helps them better grasp their genetic risks and make informed decisions about their health and the health of future generations.