If a gene from a pair of gene located at the same locus suffer a functional change is enough to create the disease, It is a sample of autosomal dominant genetic diseases At these diseases normal gene is a structural protein. Family tree has a vertical pattern. Genetic disease, in every generations, show themselves and the parents of the patient are found. The risk of this type of diseases for further generations is 50% for every pregnancy independently from the sex of children.

Contrary to classical genetic model mentioned above, many of autosomal diseases result from  de novo mutations and therefore the parents of the patient may not be found. Besides, the strength of the phenotypical symptoms may show differences between the predecessor and successor. At the person who (expressivity) or mutant gene are conveyed may not be seen the disease (loss of penetrance). Therefore diseases do not show themselves in every generations and the pattern of the tree cannot be known.

Another exemption is that the disease results from only a mutation at gamete cell of one of the parents. In this situation the disease is thought not to repeat according to transportation ratio of mutation through the cell of germs.

For autosomal dominant patients, during the consultancy these situations which go oout the model, should also be evaluated. Besides, all family members should be checked in detail.