A monogenic disease has a dominant autosomal hereditary transmission when the gene involved is located on one of the autosomes and the pathological conditions occurs when one of gene copies is altered (dominant trait); examples of the dominant autosomal diseases are familial hypercholesterolemia, polycystic kidney, neurofibromatosis, Huntington’s chorea disease. Generally individuals affected have one sick and one healthy parents.
In fig. 1 for a specific gene the normal allele is point out with a, that changed with A; for example a sick mother heterozygous Aa has both normal and mutated allele and she produces oocytes with a normal allele a or the mutated allele A; health father produces the spermatozoa with normal allele a. They can generate:
• With the probability of 50%, children with no one of mutated alleles (homozygous individual aa), so they not transmit the mutated allele, because they
have normal gene copies.
• With the probability of 50% affected children with a normal and one mutated gene (heterozygous individual Aa) so they have a probability of 50% to transmit to their children the mutated allele.
Both male and female individuals can show autosomal dominant diseases.
Fig.1- Dominant autosomal hereditary transmission