Is brachydactyly due to mutation? I have this so called "clubbed thumbs"also known as brachydactyly. It is of D-type. I searched for it on internet and found that it is a dominant inherited disease. But to my surprise,none of my family members have such thumbs.Not even my great grandfather/mother had this type of thumbs. If it is a dominant trait then why didn't it show in any other family person. Is it that I have had any mutation in my genes?

You are correct that brachydactyly is a dominantly inherited disorder and is usually caused by mutations in the BMPR1B gene.

However, not everyone who has the mutation, will have clubbed thumbs (the phenotype). This is due to a phenomenon known as `penetrance` and `expressivity`.

`Penetrance` essentially is an all-or-none phenomenon whereby certain individuals who have a mutation express the phenotype (in this case, clubbed thumbs) and some do not express it at all.

`Expressivity` is when individuals who have the mutation, will express the phenotype to varying extents. For example, only one thumb may be clubbed.

I hope this helped.