What risk is associated with a parent who has a dominant genetic disorder?

In the case of a dominant genetic disorder, if one parent carries the gene for the disorder, there is a 50% likelihood that each child will inherit that gene and consequently express the disorder. This is due to the presence of one dominant allele; even if the other allele is normal, the dominant trait will manifest. Each child has an independent chance of inheriting either the dominant or the recessive allele from the affected parent. Therefore, across multiple pregnancies, statistically, for each child, the inheritance would remain a 50% chance. This principle is rooted in classic Mendelian genetics, specifically pertaining to dominant inheritance patterns.

Other percentages represent different inheritance scenarios. A 25% chance, for instance, usually applies to recessive disorders where both parents are carriers. A 75% chance would suggest that the disorder is more likely being inherited by the majority of offspring, which does not apply here. Lastly, a 100% chance would imply that every child must inherit the disorder, which is not consistent with the principles of genetic dominance.