Final answer:
In autosomal dominant traits, a person with the disease typically has at least one dominant allele and could be either heterozygous or homozygous dominant. Conditions like Huntington's disease and neurofibromatosis type I are examples of autosomal dominant disorders.
Step-by-step explanation:
In autosomal dominant traits, nearly every person with the disease is a heterozygous or homozygous dominant individual for that particular gene. This is because in autosomal dominant inheritance, a single copy of the dominant allele (gene variant) is enough to express the trait or disorder. Examples include conditions such as Huntington's disease, Marfan syndrome, and achondroplastic dwarfism. If a person has the disease, it means they have inherited the dominant allele from one of their parents.
When considering autosomal recessive inheritance as a contrast, we find that affected individuals must receive a recessive allele from each parent, making them homozygous recessive. This means the parents are carriers of the disorder, often without showing any symptoms themselves because they have one normal gene alongside the recessive gene. In both scenarios, genetic screening and family history can provide valuable insights into an individual's genotype and potential health risks.