Autosomal dominant inheritance

An example of a family tree with an autosomal dominantly inherited trait

Basic characteristics

• refers to genes located on non-sex chromosomes – autosomes
• we observe the transmission of a trait at a conditional dominant by an allele
• phenotypicwise, the monitored trait is manifested both in heterozygotes (Aa) and in dominant homozygotes ( AA)
• in the case of incomplete dominance, heterozygotes (Aa) have less severe phenotypic manifestations than dominant homozygotes (AA), in which the respective disease manifests itself in a very severe form
• phenotypically healthy individuals (recessive homozygotes) do not transmit the mutation to subsequent generations

Genealogical characteristics

 For more information see Genealogy.

• 'both sexes are affected equally often
• typically it is vertical type of inheritance - at least one parent is affected (most often heterozygous), the disease occurs in practically every generation

Risk calculation

• when two heterozygotes (Aa) are crossed, there is a three-quarters probability (75%) of the birth of an affected offspring (in 25% of cases, the affected individual is a dominant homozygous AA)

	A	a
A	AA	Aa
a	Aa	aa

• when a recessive homozygote (aa) is crossed with a heterozygote (Aa) there is a half (50%') probability of the birth of an affected offspring (Aa)

	a	a
A	Aa	Aa
a	aa	aa

Deviations

• sporadic cases - mutation de novo (new mutation) - common for example in achondroplasia
• incomplete penetrance (the allele manifests phenotypically in fewer carriers than we would expect)
• variable expressivity (variable degree of character manifestation)
• a consequence of the external environment or other genes
• late-onset disease – polycystic kidney disease, Huntington's chorea
• mosaicism of germ cells
• nonpaternity

Examples

• Achondroplasia
• Apert syndrome
• Brachydactyly
• Familial hypercholesterolemia - frequency in the population 1:500
• Huntington's chorea - frequency in the population 1:10 000-20 000
• Marfan syndrome
• Myotonic dystrophy – myotonia, muscular dystrophy, cataract, hypogonadism, frontal baldness and changes

EKG

• Neurofibromatosis – frequency in the population 1:3 500
• Osteogenesis imperfecta
• Polycystic kidney disease - adult type, frequency in the population 1:1 000
• Polydactyly

Links

related articles

• Autosomal recessive inheritance
• Gonosomal inheritance
  • Gonosomal dominant inheritance
  • Gonosomal recessive inheritance

Exercising

• Diseases - learning about heredity

References

• THOMPSON, James Scott – THOMPSON, Margaret Wilson – NUSSBAUM, Robert L. Clinical genetics: Thompson & Thompson. 6. edition. Triton, 2004. 426 pp. ISBN 80-7254-475-6.