Visualizing carrier status: fragile X syndrome and genetic diagnosis since the 1940s

What does it look like to be the carrier of a genetic disease? Carrier status may be determined through the visual analysis of both genotypic and phenotypic evidence. Over the past 70 years, clinical geneticists have depended upon multiple strategies for identifying disease carriers within a family. This has included pedigree analysis, which was based upon clinical observations of individual family members and, in recent decades, cytogenetic and molecular methods. Newer techniques have offered novel opportunities to actually see the suspected etiological markers of certain genetic diseases, such as Fragile X syndrome. The visualization of these markers has both clarified and confused previously observed inheritance patterns, in some cases leading to the development of newly distinct diagnostic categories. As a result, what it means to be affected by, or the carrier of, a genetic disease has continuously evolved.