Chromosomes: Packing for the Genetic Journey

Mrs. Strauss had no documentation about the genetic testing performed soon after her daughter’s birth, but Dr. Banne knew the diagnosis was wrong. In trisomy 18, people are born with three rather than two copies of the 18th chromosome. No child born with it survives early childhood, much less long enough to walk into a doctor’s office at 15 years of age. So it was necessary to start from scratch. The first step was to clarify Gitti’s genetic profile by examining her chromosomes. But to fully understand Gitti’s story, we must pause here for another clarification: what are chromosomes anyway?