Expert: Dana Krempels, Ph.D. - 9/30/2010

Question
I was tracing back a certain trait I've found in my family.  My two sisters and my uncle both have what is called a "Celtic toe", or having your second toe longer than your big toe.  I've also found on several googled sites that having your second toe bigger than your big toe is a dominant trait.  The thing is is that neither of my parents have this trait, and they are both recessive- having their big toe the longest.

Is it possible for this to happen?

Answer
Dear Susannah,

Yes, it's possible.

While "Celtic Toe" (more commonly known as "Morton's Toe" or "Morton's Foot") was once thought to be a simple Mendelian trait controlled by only one gene locus, it appears that the trait may not be so simple.  The trait may be controlled by more than one interacting gene locus, and your sisters and uncle might well have inherited a combination of loci that resulted in the elongated second metatarsal characteristic of "Morton's Toe."

If this trait is not a simple case of dominance/recessiveness, its inheritance can be difficult to predict.

I hope this helps.

Dana