Counselor Preparation Comprehensive Practice Examination

What term refers to genetic disorders that are passed down through X chromosomes?

1. Autosomal Diseases

2. Y-linked Diseases

3. X-linked Diseases

4. Mitochondrial Disorders

The correct answer is: X-linked Diseases

The term "X-linked Diseases" specifically pertains to genetic disorders that are located on the X chromosome. Because males have one X and one Y chromosome, while females have two X chromosomes, the inheritance patterns can vary significantly between sexes. For instance, if a male inherits an X-linked disorder, he will express the trait because he has only one X chromosome, and the disorder is not masked by a second X chromosome that could carry a normal gene. In females, who have two X chromosomes, the presence of a normal gene on one X can compensate for a defective gene on the other X. This leads to different clinical expressions, with females often being carriers without exhibiting the symptoms of the disorder. Conditions such as hemophilia and Duchenne muscular dystrophy are common examples of X-linked diseases. Understanding this inheritance pattern is crucial for genetic counseling, as it provides insights into risks for offspring and informs family planning decisions. Other options represent different types of genetic inheritance or disorders not specifically tied to the X chromosome, helping to clarify the distinct category that X-linked diseases occupy in genetic discussions.