I used up my one allotted dumb question in med school today.

A family of patients with myotonia came to speak to us today. They have a problem with muscle relaxation and occasionally freeze up after using their muscles. The son described playing ultimate frisbee and being unable to let go of the disc. The baby girl cries with her eyes closed because she can’t relax the muscles in her eyelids. The mother is afraid to drive because her foot could get stuck and unable to brake. We watched as the squeezed their hands in a fist around a bar and struggled to let go. Interestingly, the condition worsens in the cold but improves with muscle use.

The disorder is inherited in an autosomal dominant fashion. Autosomal simply means not sex-inherited, that is, the gene does not lie on the X chromosome. Dominant means that one copy of the gene (we have two copies of every gene) is enough to cause the disease symptoms.

The family tree looked something like this:

You can see that there is someone with myotonia in every generation. Now, I was confused and asked why were there some children who did not have the disease even though their parents did. 

So, pretty much any high school or even middle school student with basic biology course can tell you the answer: Each diseased person has one disease gene and one normal gene. Thus, 50% of their children will receive the disease gene and 50% will not.

And here I am, with my biology undergraduate major and medical education asking a stupid question like that. We took our genetics final only two weeks ago and I passed with a 94%. I’m embarrassed to even go to class. I deserve to be kicked out of med school.

So yeah. No more stupid questions from me.

5/4/2