Dominant:Agenetictraitis considereddominantif it is expressedina person who has only one copy of thatgene. (In genetic terms, a dominant trait is one that is phenotypically expressed in heterozygotes).
A dominant trait is opposed to arecessivetrait which is expressed only when two copies of the gene are present. (In genetic terms, a recessive trait is one that is phenotypically expressed only in homozygotes).
Examples of dominant disorders include:
- Achondroplasia (a common form of dwarfism with shortarmsand legs),
- Familial hypercholesterolemia(highblood胆固醇导致过早冠状动脉disease),
- Huntington disease(a form ofprogressivedementia from which the folk singer Woody Guthrie suffered),
- Neurofibromatosis(NF1)(a neurologic disorder with an increased risk ofmalignanttumors), and
- Polycystic kidney disease (of adultonset).
Most dominant traits are due togeneslocated on the autosomes (the non-sexchromosomes). Anautosomal dominanttrait typically affects males and females with equal likelihood and with similar severity. The gene responsible for it can be transmitted from generation to generation and each child born to someone with the gene has a 50:50 chance of receiving the gene and manifesting thedisease.
