Is the XY chromosome mutated? What chromosome variation is it?

yes, it's an autosomal mutation! Of course, this is the result of long-term evolution. The reason why we call them X chromosome and Y chromosome is formed by chromatin condensation during its mitosis. In fact, you will find that human genomes are all X-shaped, but sex chromosomes are different. One of them has formed a V-shaped structure, which is called Y chromosome, probably due to evolution. In other animals, there are many forms of chromosomes, such as WZ, WO and so on in birds, which are the results of variation in the process of evolution. People named them in a letter-like style for the sake of illustration. In fact, human sex chromosomes are not pure V-shaped, and there are still two telomeres at the bottom of V, so they are not called V chromosomes, but Y chromosomes.