As i was looking through my notes, I saw that there is reproductive abonormality where one is born with an XY chromosome (not X and Y, but together!), this causes a person to be male for example and have the secondary features of a female. This really made me think and curious as to how this happens. I went online to search for answers and found:
"explanation of this rare phenomenon is a parthenogentic division of a haploid ovum into two haploid ova. Upon fertilization of the two ova by two sperm cells (one carrying an X and the other carrying a Y chromosome), the two fertilized ova are then fused together resulting in a person having dual genitalial, gonadal and genetic sex."

I thought this was very interesting and made me think of the other abnormalities that we learned of. I just wonder why these things happen and how they can occur, nature is so flexible