Final answer:
Humans with an XXY karyotype are considered male, having Klinefelter syndrome, while fruit flies with the same karyotype are female, as the sex in fruit flies is determined by the ratio of X chromosomes to autosomes.
Step-by-step explanation:
Individuals with an XXY karyotype are male in humans and female in fruit flies.
In humans, the presence of a Y chromosome typically determines a male sex determination. Therefore, individuals with an XXY karyotype have one type of Klinefelter syndrome, which is associated with male characteristics, although individuals may exhibit physical traits such as small testes, enlarged breasts, and reduced body hair. These individuals are considered male despite the additional X chromosome, which undergoes inactivation to prevent excess genetic dosage. In fruit flies (Drosophila melanogaster), the sex is determined by the ratio of X chromosomes to sets of autosomes, not the presence of a specific sex-determining chromosome like the Y. Normally, the ratio of two X chromosomes to two sets of autosomes (XX:AA) results in a female fly. Therefore, an XXY fruit fly is female because it has a higher ratio of X chromosomes (XX:AA versus XY:AA in males).