The genetic matter that exists within the human cell is inherited from the parent to the offspring. Several of your features might resemble your parents – your hair color, the color of your eyes, etc. The process through which you receive these traits is called inheritance.
Autosomal dominant disorders are inherited conditions that are passed down from generation to generation following a specific pattern.
Let us break down the inheritance pattern for Autosomal dominant disorders for you.
The human body has two types of chromosomes – Sex chromosomes and non-sex or autosomal chromosomes. In autosomal dominant disorders, the gene in question is located on the non-sex chromosomes.
Now, there are two types of genes. Dominant and recessive. Recessive genes need two copies of the gene for the trait to be fully expressed. For instance, if one parent contains a recessive gene ‘b’ for blue eye color and the other does not, the offspring will not have blue eyes. However, if both the parents contain the recessive gene ‘b,’ there is a 25% probability of the child having blue genes.
In dominant genes, a single copy of it is enough for the trait to be expressed. Say a parent has dominant gene ‘B’ for blue eyes and the other does not; still, the offspring will be able to show blue eyes.
In autosomal dominant disorders, the mutant gene or the gene carrying the disorder is present on the dominant gene. A child of a person affected by any type of autosomal dominant disorder bears a 50% chance of bearing that disorder.
Let’s now discuss the types of autosomal dominant disorders:
1. Huntington’s Disease
As per research by Tamara Pringsheim and team, the prevalence of Huntington’s disease (HD) was 2.71 per 100,00 people. HD is a rare inherited neurological degenerative disease that causes the breakdown of the nerve cells present in the brain. It has a wide-ranging impact on a person’s cognitive and functional abilities. It further leads to:
- movement disorders: involuntary jerking, unusual and slow eye movements, etc.,
- cognitive malfunction, and
- psychiatric disorders: depression, aggressive behavior, etc.
Neurofibromatosis is a group of autosomal dominant disorders that causes tumors to develop on the nerve tissue. The tumors can originate at any place in the nervous system, including the brain, nerves, and spinal cord.
There are three different types of Neurofibromatosis:
- Neurofibromatosis 1 (NF1): This type is usually diagnosed in childhood. Flat, brown spots on the skin, tiny bumps on the iris, deformities in bones, etc., are signs of the disorder.
- Neurofibromatosis 2 (NF2): The prevalence of NF2 is less than that of NF1. The onset is generally marked by benign and slow-growing tumors that damage hearing abilities significantly.
- Schwannomatosis: This rare type of autosomal dominant disorder generally affects people after age 20. This causes tumors to develop on cranial and spinal nerves rather than around the ear or in the brain.
3. Myotonic Dystrophy
Myotonic Dystrophy (MD) is the most prevalent form of a group of disorders called muscular dystrophy that begins in adulthood. It is marked by muscle weakness and progressive muscle wasting. These people have prolonged muscle contractions. For example, a person with MD might have a problem with releasing the grip of a doorknob.
Other common signs of the disorder include:
- abnormalities in electric signals that control heartbeat,
- clouding the lens of the eye,
- delayed development, etc.
Even though it is impossible to prevent autosomal dominant disorders, various tests are available that might indicate probable risks. While planning for a family, talk to your healthcare provider and understand the risk of genetically linked disorders that run in your family. A genetic counselor will be able to walk you through the test process properly.
Do you know that not just physical diseases but mental illnesses have been found to have a genetic link to them? To learn more about the genetic inheritance of mental illnesses, click here.
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