I always wonder where they get their unwarranted confidence from. This person seems to have confuse the Y chromosome with the entire genetic complement, or something. I don’t want to have to untangle their thinking right now.

That’s not how DNA works. Your brother would have his father’s DNA and his mother’s DNA. You, as a girl, would have your mother’s DNA and your father’s mother’s DNA. You have only half of your father’s DNA. You do not have your father’s father’s DNA.
And this is why (if one’s father has any brothers) it’s difficult to prove a girl’s paternity. All the brothers would have the same X chromosome so any brother could be the father. It’s been pivotal in the Thomas Jefferson/Sally Hemmings controversies.
You don’t necessarily have the same X chromosome as your brother. It’s not hard to figure out a girl’s paternity because there are all these autosomes. I think someone got a vague hint of how sex is inherited and garbled everything up beyond that. But they still get to tell someone else they don’t understand how DNA works!









