Autosomal dominant inheritance is one of the simplest models for genetic counseling in theory. But it is one of the most problematic topics in practicals. You can determine an autosomal dominant disorder, by its pattern of inheritance in a family and with the help of an autosomal DNA test.
The probability of an offspring being born with a disease is one-half. That is 50% regardless of gender.
Almost most of the autosomal dominant patients are heterozygotes. This meant they got their illness only from one side of the family or had novel mutations. In homozygosity, both parents have to pass on the defective gene.
This is rare unless one of the following conditions exists:
The gene is prevalent and has generally modest or late-onset symptoms.
Two people with the same disease have married.
In this, the pattern looks like an autosomal dominant disease at first. But when you examine the offspring of an affected man, you will see that all the males are fine, but the females have the disease. A DNA test is one of the ways you can figure this condition out with.
In X-linked illnesses, it is difficult to find differences between dominant and recessive. In rare cases, heterozygotes may have the disease in one branch of the family but not the other. To better understand the problem, you can look at the inheritance pattern. In the children of afflicted men, girls are either affected, or carriers, but there is no effect on boys. DNA testing is the only way to figure it out.