In this activity, students apply their understanding of sex-linked inheritance to diagnose and treat an alien species affected by a recessive X-linked trait. The student analyzes the pedigree chart to track the transmission of the trait across generations, identifying affected individuals and potential carriers. By distinguishing between males (XY), who express the trait if their single X chromosome carries a recessive allele, and females (XX), who must inherit two recessive alleles to express the trait, the student determines which aliens require a special serum. Using labeled pedigree markers, they allocate the limited supply of treatment, reinforcing concepts of sex-linked inheritance and genetic prediction.