subject: How Do We Inherit Genetic Disorders? [print this page] A genetic illness can be caused by mutations in one single cell. There are six different patterns by which genetic disorders can be inherited, depending on which gene is involved. Genetic diseases can be inherited by Autosomal dominant, Autosomal recessive, X-linked dominant, X-linked recessive, Codominant and Mitochondrial.
In Autosomal dominant, having one altered copy of the gene suffices for an individual to be afflicted by an Autosomal dominant disease. The person affected by it has one parent who is also affected. Scientists concluded that Autosomal dominant illnesses happen in every generation of an afflicted family. Belonging to this group are diseases such as type 1 neurofibromatosis and Huntington disease.
When two copies of a gene are mutated and present in each cell of an individual, then, Autosomal recessive is the pattern by which the genetic disorders follow. In such pattern, the individual affected by it has parents who are not affected but each carries a single copy of the changed gene. Here, the parents are called gene carriers and the Autosomal recessive disorders do not occur in every generation of an afflicted family. Diseases that have Autosomal recessive pattern are cystic fibrosis and sickle cell anemia.
For a genetic disease to be labeled X-linked dominant, the gene mutations must occur on the X chromosome, and thus make women more vulnerable to developing diseases such as fragile X syndrome. Also, the chance of passing on the X-linked dominant illness varies between women and men. However, in each generation of the affected family, both men and women are often affected. One curious characteristic of an X-linked dominant illness is that men cannot pass on the disorder to their sons.
In X-linked recessive illnesses, the gene mutations also happen on the X chromosome. However, the difference is that here, the males are more vulnerable than the females. And although the chance of passing on the disease varies between males and females, in affected families, males are often affected in each generation. Also, sons cannot inherit from their fathers the X-linked recessive illnesses like the hemophilia and Fabry disease.
The Codominant disease has two distinct versions of genes being expressed, with each version having a miniscule variation in protein. Nevertheless, both genes affect the genetic characteristics of the condition. An example of disease considered to have Codominant pattern is the alpha-1 antitrypsin deficiency.
Another term for Mitochondrial pattern of obtaining the genetic disorders is the maternal inheritance, which refers to the mutated genes in mitochondrial DNA. The mitochondria convert molecules into energy, with each molecule containing small amount of DNA. Only women can pass on the mitochondrial mutations to their offspring because only the egg cells contribute mitochondria to the developing embryo. Illnesses following the Mitochondrial mutations can occur in every generation of the affected family. They also affect both men and women, however, children inherit the Mitochondrial genetic disorders from their mothers alone.
Besides the patterns mentioned above, other illnesses are caused by interactions between the environment and genes or by combining the effects of several genes. These illnesses are hard to analyze due to bleak genetic causes. Examples of such diseases are diabetes, schizophrenia, heart diseases and some cancers.
