Genetic mutations

What is a mutation?

Each gene is formed by the chains of bases, and the arrangement of these bases provides instructions to form single proteins. Any change of this chain - and therefore of protein instructions - is called a polymorphism or a mutation. In the same way as an exchange of the words in a sentence may change its meaning, a mutation may change the instructions of the gene. Some changes of a sequence of bases have negligible or almost no effects on proteins - these are called polymorphisms - whereas other changes cause a protein to completely fail to perform its function - these are called mutations.

How a mutation occurs?
In the course of life, everybody undergoes changes of their DNA. The cause of these changes is multifactorial. Each time the cell is divided, all its DNA is doubled, so that each cell contains a complete set of DNA.

In some cases, simple errors in copying occur during this process. Other changes may develop as a result of impairment of DNA because of environmental and lifestyle effects, such as sunshine, smoking or radiation.

Our cells contain incorporated mechanisms which may take up and correct many of these changes. Nevertheless, as we grow over time, these mechanisms stop working effectively and the changes are acummulate in our DNA. Some of them occur in the cells of our body – e.g., in the cells of our skin as a result of exposure to sunshine. However, these changes are not inherited. Other disorders occur in the DNA of reproductive cells – eggs and sperms, and they may be transferred from the parent to the child. If a child inherits such a mutation from the parent, each cell of his/her body will contain this disorder in its DNA.

What problems can mutations or functional polymorphism cause?
Some mutations, or so-called functional polymorphisms, cause proteins not to work as they should and may cause a disease.
Some mutations affect a protein that is not able to work normally or sufficiently in the cell. Phenylketonuria is an example of this type of mutation. A protein called phenylalaninhydroxylase, which works as an enzyme, is impaired in this disease. The functionless enzyme, which is necessary for the body to metabolize phenylalanine, causes this aminoacide to accumulated and not to be eliminated from the body. It results in a serious disease called phenylketonuria.

Another example is haemophilia. In this case, the mutation causes an absence of the protein that is responsible for coagulation of blood. It results in uncontrolled bleeding during any injury.

Polymorphisms and mutations affecting DNA expression
There are many types of polymorphisms and mutations which do not change the protein itself but only its quantity. These types of changes in DNA may result in the wrong timing of the production of a protein, in the wrong quantity, or at a wrong place. The changes may cause insufficient production or overproduction of a protein. This very type of polymorphism affects predispositions to most civilization diseases, and therefore the GenScan test panel consists of an analysis of this type of polymorphism in particular.