If the alteration concerns information contained in the gamete, it is passed on from generation to generation. In the case of changes contained in somatic cells, diseases are not inherited, but a higher risk of a particular disease is possible.

In Poland, approximately 20 000 children are diagnosed with a genetically determined disease each year. In the case of autosomal dominant inher itance, the incidence of the disease does not depend on gender. Healthy offspring of a patient always have healthy children. The probability of passing the gene to offspring is 50%.

With regard to autosomal rec essive inheritance, the mutated recessive gene does not manifest itself in the presence of a normal dominant allele. Symptoms are manifested in both sexes and the risk of having a sick child is 25%. The probability of a healthy child being a carrier is 2:3.

X-linked diseases can be inherited as a dominant or recessive trait. In the case of dominant inheritance, both men and women show symptoms of the disease. Heterozygous women have a 50% risk of passing the gene on to their offspring. Heterozygous men pass on the mutated gene to their daughters. In recessive inheritance, only men show symptoms. Heterozygous women bear a 50% risk of passing the gene to offspring. Affected men pass the gene on to their daughters.