Final answer:
The disorder with a 50% occurrence rate in both males and females determined by a nurse at a genetic counseling center is most likely an autosomal dominant disorder due to the equal rate of occurrence in both sexes.
Step-by-step explanation:
The nurse in a genetic counseling center determines that a disorder with a 50% occurrence rate in both males and females is most likely an autosomal dominant trait. If a disorder were X-linked recessive, males would be affected at a higher rate than females, because males only have one X chromosome and thus a single copy of the X-linked recessive gene would result in expression of the disorder. Females, with two X chromosomes, would need two copies of the recessive gene to express the trait, making it less likely for them to be affected. Hence, with an equal occurrence rate in both genders, and ruling out chromosomal trisomies that have different patterns of inheritance, an autosomal dominant disorder is most consistent with the given scenario.