This statement is true.
In the case of autosomal dominant disease, the person is either homozygous (which is very rare) or heterozygous. On the molecular level, either the mutation produced a new deleterious protein for the organism, or the mutation affected an existing protein in the physiological state and that a 50% activity is not enough to compensate for the needs. of the body.
In case of autosomal recessive disease, the sick person is always homozygous. If the two loci each have a different mutant allele, it is called a "composite heterozygote". People with autosomal recessive inheritance disorder have "mandatory heterozygote" parents.
