cut in half and slightly souped up

There are certain advantages to being a man. More upper body strength means you don’t have to find someone to help you lift the flat tire you just changed all by yourself into the trunk, even though you know how to do the whole thing by yourself but just aren’t strong enough to pick up the dang tire (what, I’m not bitter). Negotiators take men more seriously (not saying it’s fair, but it’s true). Men are statistically way less likely to be mugged or assaulted. But at the end of the day, men are inherently lacking in an area that women aren’t: genetic material.

Female allosomes on left, male on right. Notice the DINKY,
 LITTLE, Y. (http://www.brusselsgenetics.be)

You have 23 pairs of chromosomes- one of each pair coming from one parent. One pair represents your allosomes, aka “sex chromosomes.” If you’re a boy, you got a “y” chromosome from your dad and an “x” chromosome from your mom. If you’re a girl, you got an “x” from your dad AND an “x” from your mom. So, girls= xx and boys = xy.

That Y chromosome is really key in determining sex. It is way smaller than the X chromosome, and doesn’t really carry too much information on it aside from the most vital male-determining genes. It contains a gene, called the SRY gene, that “turns on” maleness/testosterone production. You see, being female is like the default condition. The presence of a y chromosome lays the groundwork for being male, but the activation of its SRY gene is what actually drops the ball(s). (Which, by the way, are really ovaries that were told to descend and produce sperm by the SRY gene). So, morphologically, all embryos start off as female and then are changed into male once the Y chromosome kicks into action.

The X chromosome carries way more DNA, including sequences that are not directly sex-relevant.  Yes, there’s DNA for instructions on building ovaries and eating Ben and Jerry’s once a month (don’t forget, men have this too on their X chromosome, but that Y turns on the maleness that covers up the female condition). But there’s also genes for more unfortunate things like the recessive male-patterned baldness and colorblindness.

Women carry these genes all the time. But since they’re recessive, the trait is not expressed unless a very unlucky lady happens to get them on BOTH her X’s. And that’s just not very likely. But if a female who has colorblindness in one of her X chromosomes gives that X to her son, he’s screwed. That scrawny little Y from dad doesn’t have enough punch to combat the trait like a girl’s extra X would. This is why color blindness and male-pattern baldness are almost exclusive to men. Since he got the X from his mother, he knows that one of her parents is responsible. If it was her dad, he will have expressed the trait. This kind of inheritance is called sex-linked inheritance.

So really, an XY is just a cut-in-half and then slightly souped-up version of an XX. Ladies, we may not have enough testosterone to lift a tire into the trunk, but we have enough DNA to keep colorblindness and pattern baldness at bay. We win… this one.