types of autosomal inheritance

Last reviewed 01/2018

Autosomal dominant inheritance is characterised by manifestation of the disorder in either the homozygote or the heterozygote that carries the allele.

There would be expected to be a segregation ratio of 1:1 in the offspring of an affected heterozygote and a normal partner. Hence, more offspring tend to be affected than in autosomal recessive disorders.

As with autosomal recessive disorders, both sexes may be affected, but, there may be different degrees of severity - variable expression - between individuals.

Rarely, an individual with a mutant gene may have a normal phenotype. This is termed 'non-penetrance'. The gene and trait may still be transmitted to the individual's offspring.

About 2200 autosomal dominant traits are known to date. They tend to be defects of carrier, structural or receptor proteins. The most common autosomal dominant diseases are:

disorder incidence/1000 births

• dominant otosclerosis 3
• familial hypercholesterolaemia 2
• adult polycystic kidney disease 1
• multiple exostoses 0.5
• Huntington's disease 0.5
• neurofibromatosis 0.4
• myotonic dystrophy 0.2
• congenital spherocytosis 0.2
• polyposis coli 0.1
• dominant blindness 0.1
• dominant congenital deafness 0.1