Final answer:
The sex chromosome constitution of a male duck-billed platypus is peculiar, featuring multiple X and Y chromosomes, specifically X1Y1X2Y2X3Y3X4Y4X5Y5, distinguishing it from the conventional mammalian XY or avian ZW sex-determination systems.
Step-by-step explanation:
The sex chromosome constitution of a male duck-billed platypus is X1Y1X2Y2X3Y3X4Y4X5Y5. Unlike most mammals which have the XY system, or birds which use the ZW system, the duck-billed platypus has a complex sex chromosome system with multiple X and Y chromosomes.
In most mammals, the sex is determined by the XY sex-determination system, where males have one X and one Y chromosome (XY), and females have two X chromosomes (XX). Birds typically use the ZW system, where males are ZZ and females are ZW. However, the platypus, as a monotreme, differs from both systems.
For platypuses, it is not a straightforward XY or ZW system. Platypuses possess ten sex chromosomes, with the males having five X and five Y chromosomes. This is unique and not seen in any other mammalian species. The presence of multiple sex chromosomes leads to complex inheritance patterns, where sex determination is still an active area of research.