Chapter 14 Case Study: Genetic dwarfism Seven months pregnant, an expectant mother was under-going a routine ultrasound. While prior tests had been normal, this one showed that the limbs of the fetus were unusually short. The doctor suspected that the baby might have a genetic form of dwarfism called achondroplasia. He told her that the disorder was due to an autosomal dominant mutation and occurred with a frequency of about 1 in 25,000 births. The expectant mother had studied genetics in college and immediately raised several questions. How would you answer two of them? 1. How could her baby have a dominantly inherited disorder if there was no history of this condition on either side of the family? 2. Is the mutation more likely to have come from the mother or the father?