This is a great question. It can be hard to think about how this could happen. If the parents have dwarfism, the kids should too, right?

Well, no. This is only true of recessive traits. Dwarfism is most commonly a dominant trait.

Very useful answer, huh? Let's dig a little deeper to find out what the answer really means.

We have two copies of most of our genes -- one from mom and one from dad. And our genes can come in different versions called alleles.

For example, there is a gene called FGFR3. Most people have versions of this gene that result in average height. But some versions can lead to dwarfism.

People with dwarfism have one copy of FGFR3 that causes dwarfism and one that does not*. In genetics speak, this means that the dwarfism version is dominant to the other, more common version.

Now imagine two parents with dwarfism. Which copy of a gene we get from our parents is random. So for this discussion, each parent has a 50-50 shot of passing down a copy that does not lead to dwarfism.

What this means is that 25% of the time, the child will get a copy of the average height gene from both parents. The result will be a child of average height.

So that explains that. Two parents with dwarfism can have a child of average height because the parents are carriers of that trait.

But wait a minute. If dwarfism is dominant, where does it come from in the first place? Do people with dwarfism always have little people as parents? No.

Around 7 out of 8 cases of dwarfism result from DNA changes in the FGFR3 gene that appear out of nowhere. Literally. These changes (or mutations) happen in the sperm or the egg or very early on in development.