Autosomal Recessive Inheritance

There are many diseases that one tends to incur due to some genetic disorders. Autosomal recessive inheritance means inheriting genetic diseases from both the parents, wherein, the genes of both the parents contains an abnormal gene which makes the child prone to inherit autosomal recessive diseases and disorders. Confused? Let us break of up the term in order to understand its meaning in a clear way! Autosomal refers to the error that occurs among any of the first 22 chromosomes, excluding the 23rd sex linked chromosome! The term recessive, means that the affected person should have 2 copies of the bad or affected gene, one from each parent, in order to inherit the genetic disease. So, overall, autosomal recessive inheritance means, inheritance of 2 copies of an abnormal or affected gene, which leads to development of a genetic trait or disease!

Inheritance of Autosomal Recessive Genetic Diseases

The inheritance pattern is very clear and there are rarely any scenarios wherein a person inherits an autosomal recessive disease. This is because, it is necessary for the person to inherit both the affected genes, each from the father, and the mother. For this, both the parents should have one abnormal gene of the same disease, which is a rare scenario! However, it is possible for both the parents to be the carrier, which means, that they have one affected gene and one healthy gene. In spite of having an affected gene, the parent may not have the traits or diseases, because the healthy gene can balance the health of the person. Mentioned below is the pattern of inheriting autosomal recessive genetic diseases, and how it usually works.

• If both the parents are carriers, meaning, they have 1 abnormal gene each, then there are 25% chances that the child will have a disease (have both abnormal gene from each parent). On the other hand, there are 50% chances that the child will be a carrier (have one affected gene and one healthy gene, but have no disease), and again, there are 25% percent chances that the child will neither be the carrier, nor have the disease (have both the genes healthy).
• If only one parent is the carrier, and the other parent is unaffected, then there are 50% chances for the child to be the carrier, however, in no way can he / she be affected by the autosomal recessive traits or diseases.
• If one of the parent is a carrier, and the other parent has the autosomal recessive disease, then there are 50-50 chances for the child to either have the disease, or be the carrier. In any case, he will not be unaffected and will either be the carrier or be affected by the disease!

To explain it in a better way, let us take an example. Say for instance, there is a couple, who both carry the abnormal gene, but are not affected by the disease, meaning they are just the carriers and do not have the disease. What can be the chances of their children suffering from autosomal recessive diseases? Let us say that they have 4 children, the pattern of autosomal recessive inheritance would be,

• 1 out of the 4 children will have both normal genes, meaning he will be unaffected!
• 2 out of the 4 children will contain one normal and one abnormal gene. Which means that they will be carriers but will not have the disease!
• Lastly, 1 out of the 4 children will have both abnormal genes, that means he might inherit the disease!

Some examples of autosomal recessive inheritance diseases include, Sickle Cell Anemia, Osteogenesis imperfecta (brittle bone disease), Cystic Fibrosis (affects secretory glands), Congenital Neutropenia (blood disorder), Alport Syndrome (kidney disease), etc.

A point to be noted is that not all genetic diseases and disorders are related to autosomal recessive inheritance! An example for the same would be the 'Sporadic Genetic Disease', which can occur in children, in spite of no genetic abnormalities in the parents. In order to call a disease autosomal recessive, the genes of both the parents should be affected. Another important point here is that this condition is not gender biased, meaning, it can be found in both males and females because the abnormality does not occur in the 23rd sex chromosome. However, there are some exceptions wherein children have inherited genetic disease with only one parent being the carrier, however, that is a very rare scenario! Researchers are still trying hard to explore the many facets about the human genes, many facts that are unexplored will soon come into light as technology advances.