Seven months pregnant, an expectant mother was undergoing 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 them?
If this child has achondroplasia, is there an increased chance
that their next child would also have this disorder? Why or
why not?
Could this disorder have been caused by X rays or ultrasounds
she had earlier in pregnancy?