Bringing Diagnosis into Focus: The Problem of Missing and Extra Genes

Some genetic conditions have distinct symptoms that make clinical diagnosis relatively straightforward. Others are more mysterious. Similarly, lab tests used to confirm a physician’s tentative diagnosis have differing levels of complexity, depending on how the suspected condition would be reflected in the patient’s genetic material. For example, the extra 21st chromosome of a child with Down syndrome, or that deleted section of the 18th chromosome in the case of Gitti, are both plain to see in a karyotype test, in which a patient’s chromosomes are lined up for visual analysis.