Author notes

033. Gene Therapy

usedbooks

on May 10, 2009

Q: How do you tell a boy chromosome from a girl chromosome?
A: Pull down its genes!

My mom taught me that joke as a trick to remember that genes are on chromosomes. The "characters" in today's comic are chromosomes because I couldn't think of a way to draw genes so they would be recognizable. A gene is a piece of coding DNA around 10 to 15 kilobases in length (in humans). Each chromosome contains many genes (but mostly non-coding or "junk" DNA). Chromosomes get their name from the fact that they show up very dark when a cell undergoing mitosis is stained (chroma = color, soma = body). During this process, they are 'X' shaped (two chromatids, connected at a centromere). When not undergoing mitosis, DNA is not packed tightly but loosely arranged so it can be 'read.' (If you've had any biology classes, you probably know all this or learned it and forgot.)

Btw, Y chromosomes have no "mother." The same Y chromosome has been passed down from father to son since "Adam." – Scientifically, "Adam" is the first individual to possess the Y chromosome present in all human males. "Eve" is the individual who first had the mitochondrial DNA present in all humans (of both sexes). Mitochondria always come from your mother because the male gamete (sperm) contributes only genomic DNA, no mitochondria or other cellular material.

The deviation from my usual strip format is because this comic is a Mother's Day gift. When I was a kid, I drew single panel comics like this, and my mom loved them. So, happy Mother's Day, Mom! Thanks for the genes (and the mitochondria, and the incessant, albeit useful, advice)!