Autosomal Dominant Inheritance
Genes are the blueprints for making proteins. Our bodies need proteins to develop
and work properly. Most genes come in pairs. One is inherited from the mother and
the other from the father. Genes inherited from our biological parents are expressed
in specific ways. One of the these basic patterns is called autosomal dominant inheritance.
What is autosomal dominant inheritance?
There are two types of chromosomes:
Sex chromosomes, which determine male or female gender
Autosomes, which are all of the other chromosomes (chromosome pairs 1 through 22) or non-sex
Autosomal inheritance of a gene means that the gene is located on one of the autosomes.
This means that males and females are equally likely to inherit the gene. "Dominant"
means that a single copy of the gene can cause a particular trait, such as brown eyes
instead of blue eyes. When a parent has a dominant gene, there is at least a 50% chance
that any child he or she has will also have the trait.
There are 4 possible combinations in the children.
These combinations are possible every time a pregnancy occurs between these 2 individuals.
The gender of the children (whether they are sons or daughters) does not matter. The
chance is 50/50 for them to inherit the autosomal genes.
A characteristic of some dominant genes is that they can have variable expression. This
means that some people have milder or more intense characteristics than others. Another
important characteristic of dominant genes is that in some cases, they can have reduced
penetrance. This means that sometimes a person can have a dominant gene copy but not
show any signs of gene. The concept of reduced penetrance is particularly important
in the case of autosomal dominant cancer susceptibility genes. If a person has inherited
a cancer susceptibility gene, it does not mean he or she will automatically develop
cancer. It simply means that the person has inherited a mutation in a gene that gives
him or her a higher chance to develop cancer than someone without the mutation.
Examples of conditions involving autosomal dominant inheritance includes Marfan syndrome,
Ehlers-Danlos syndrome, Neurofibromatosis, and achondroplasia.