Color Blindness is an X-LINKED gene.

I got into a "discussion" with a girl who "knows everything."  I met her; within five minutes she walked in "owning MY house" or acting like it, told me that my recent break-up was unimportant (I wasn't talking to her about it) and said that I had no idea what I was talking about when it came down to color-blindness.  P.S. I still have no idea how all of it came up, because I don't even know her, therefore I wasn't talking to her.

• The relationship part, I have no idea where it came from because no one (8 people were around) was talking about it.  
• The color-blindness part, I think everyone else was talking about color-blind people. Well Miss Know-it-all said that girls are lucky because we can't get color blind, ever; because it can't run in the XX genes.  I told her that girls can, and she said that she knew as a fact that it is IMPOSSIBLE for girls to get the trait because it is carried on the Y chromosome.  I didn't want to be mean and tell her that I have had five (now six) different classes to say otherwise.  Today I have started a chapter in anatomy about genes, and how things are passed on.  Here is an exact quote from my book.  "Most sex-linked traits are carried on the X chromosome.....Examples are hemophilia, certain forms of baldness, and red-green color blindness."  The reason that it is more common in boys is because the Y chromosome is smaller that normal chromosomes and X chromosomes are larger than normal.  The CB trait shows up on the X chromosome as recessive, and the Y chromosome doesn't have a dominant trait to reverse it so the child (boy) is color blind.  If the CB trait shows up on two X chromosomes (girl) the child is color blind, but it is extremely rare for it to have two recessive CB genes.  

I am sure that you all think this is pointless and petty, but I needed to vent somewhere and say HA! Maybe because Aunt Flo has come to visit.  Maybe it all pissed me off, because I had a complete stranger tell me that my relationship, where I almost married the guy, was unimportant. Rude.