Genetics
Urea cycle disorders are inherited inborn errors of metabolism. They are caused by defects in the genes that code for enzymes or membrane transporters that are needed for the production of urea from protein. They are inherited in one of two ways — either through X linked chromosomes or through recessive chromosomes.8
Ornithine
Transcarbamylase Deficiency is inherited through an X linked or sex linked chromosome.
This means the mother has a defective X chromosome that is passed on to her son.
Since males only have one X chromosome, if it is defective, they will have the
disease. Mothers can also pass on a defective X chromosome to their daughters,
but since women have two X chromosomes they will either be asymptomatic carriers
or have milder forms of the disease.
The other urea cycle deficiencies are inherited through recessive genes. These are non-sex-linked chromosomes, so each person has two. Both parents must have a defective gene for the same urea cycle enzyme deficiency to appear in their children. The affected child will have two recessive genes for the disease. Other siblings may receive one defective gene and be asymptomatic, or may receive no recessive genes.
References:
8. Manson, Ania C, Cell Biology and Genetics, Mosby, Edinburgh, 2002, p.144-153.