on being the child of my parents.

Every so often, a family joke comes up after someone (usually me) cries "OW! That HURT!" After I do something graceful like fall off the deck, or catapault myself down the hill behind our home on roller blades, or, you know, fall on concrete while...get this...walking.

"Well, at least we know that your mother didn't sleep with the mailman!"

You see, my father's head is peppered with the results of various infraction involving tools, or car hoods, his arms showing that yes, he knows what it's like to hit your arm against a hot engine that's still running. He shuns any attempts my mother made to avoid infections, and his scars show the storied history of a man talented at being a bit too busy working to notice such paltry things as sharp edges.

This is very much something I inherited from my father. And the only reason I don't have such a menagerie of injuries is because I don't work with things that are so --dangerous-- well...most of the time.

I know that the oven hood is there. I know that there's a corner edge there as well. But whether it's the inability to accurately judge space or an intensity on the task at hand or just plain and simple that my spatial perception is terrible...I don't really know.

My mother and I look very much alike, and this frustrated me time and again when I was younger. "Oh she looks so much like J!" "Oh that hair! I can't believe her hair. She looks exactly like you!" "Spitting image!" I guess what bothered me was that they weren't talking about me as myself...they were talking about my similarity to my mom. And as a kid, you don't realize that this is sometimes a compliment (I definitely take it as one now!) But yes...it's funny to think that even with all we know about genetics, there is a lot we don't understand.

Biologically speaking, each female on this earth contains two X chromosomes, one from her father, and one from her mother. Every male has one X chromosome from his mother and one Y chromosome from his father. (keep in mind that there are many reasons gender can be defined and explained, which is an entirely different discussion). But --- there is an important step that happens to every cell in the female body called X inactivation. In any given cell, only one X chromosome can operate at any given time, and this choice is made randomly. This means that some of my cells are more related to my mother, while some are more related to my father. If you called my mother "blue" and my father "purple" you could see me as some sort of mottled spotted thing; almost like a calico cat. This is called mosaicism (like a mosaic; it's the first option below).


from New England Journal of Medicine's article entitled X Inactivation in Females with X-Linked Disease, 1998

Other things can happen, of course. Mutations on either of the X chromosomes could preferentially result in having all Xs belong to your mom (middle) or your dad (bottom). But this isn't normal...what is normal is being a blend of both your parents, and different parts of a female's body have different slants towards either parent. However, it is important to remember that you have a bevy of other chromosomes that are present and active in all of your cells (22 from each parent) so that's why we don't have mottled hair color like calico cats (the gene for hair color is on the X chromosome in cats; it is not for us). However, 2000 genes are on this chromosome, and this can contribute to specific diseases (more often in boys) but also to X-linked diseases in girls.

New research has also shown that these inactive Xs may not be as inactive as we thought, yet this is a fundamentally intriguing idea...it posits that idea that males are more related to both parents than females. For women, however, this mosaicism appears to random, which means I very well could have patches in my brain that operate more on my father's wavelength than my mothers (although, again---this could also be due to differences in the other 22 chromosomes). What does this have to do with mailman issue? Well, based on a lot of different things in how I think, there are parts of my brain that seem to bend one side over the other...and it's an interesting idea to think of how and why I am like either of my parents.

And this doesn't even bring in the nurture side of the equation. Oh biology...your complexity keeps me on my toes.