Negative Mitzvah 352
Prohibition against an uncle-nephew relationship
Leviticus 18:14 "Do not act immodestly with your father's brother"
It is forbidden to act immodestly with your father's brother (your uncle).
Negative Mitzvah 347
Prohibition against marriage with a married woman Exodus 20:13 "You shall not commit adultery"
A person is not allowed to act immodestly with another man's wife.
Negative Mitzvah 346
It is forbidden to come into physical contact with a "Niddah"
Leviticus 18:19 "Do not come close to a woman who is a Niddah"
"Niddah" is a specific personal condition which can only apply to a woman. A man is not allowed to have physical contact with a woman who is considered "Niddah."