1. Discuss why only trisomies of chromosomes 21, 13, and 18 are seen in live births, and why these reduce the life span, often drastically. Why aren't trisomies of larger chromosomes able to produce a live individual?
2. Discuss the methods of prenatal diagnosis and the means of recognizing carriers so that couples at risk for having a homozygous recessive child will know to test for a particular disorder.
3. Consider the possible effects of an X-linked disease
on a carrier female, given the random inactivation of one X in
each cellóhalf her cells would be expected to have the
abnormal X active. Think about color blindness, for example, or
Duchenne muscular dystrophy.