A related more general mnemonic works for the running lights too. Red has fewer letters than green, so it goes with left which has fewer letters than right and port which has fewer letters than starboard.

YY is non viable; the X chromosome has many genes which are essential. You can be XY, female, and fertile, but it’s pretty rare.

There’s a bunch of them, but one more common example is Androgen Insensitivity Syndrome.

It’s also possible to have a non-functional SRY (XY but female), or to be XX with an SRY translocation (XX but male).

Biology is complicated: pretty much anyone who says it only happens one way or is really simple is wrong.

shutdown: command

That didn’t work out so well.