We are in the final laps of the A-to-Z Challenge, which means today’s post is about the “X” chromosome. First, a little genetic refresher about the sex determining 23rd pair of chromosomes: females have two “X” chromosomes and males have an “X” and a “Y”….. but more about the “Y” tomorrow.
Here are some facts about the “X”:
- The “X” holds about 2,000 genes. (vs. the “Y’s” 78 genes. Again, stay tuned tomorrow)
- The “X” is somewhat mysterious. Females deactivate one of their “X” pairs, but scientists are not sure why.
- The “X” holds an enormous amount of genetic diversity (and you know what Darwin had to say about that) because each copy of the X chromosome contains versions of genes not found on its partner.
- Even though the “Y” is what determines male from female, there is stuff on the “X” that’s needed to support cellular activities required to actually make a boy, like androgen receptor. Here’s a link to an expert, Jessica Profato of Stanford University, giving a far more elegant lesson in simple language — Understanding Genetics. In all fairness she’s answering an elementary school student’s question, but I have no recollection of discussing this in my 5th grade science class.
Genetics is fascinating. It’s what gives us the physical specimens of supermodels and super athletes. It’s random and magical that humans are still making people with this one sperm and one egg technology — it is the original DIY project.*
* OK — technically you have to work with a lab partner.