Critical to the accurate diagnosis of human illness is the need to distinguish clinical features that fall within the normal range from those that do not. That distinction is often challenging and not infrequently requires considerable experience at the bedside. It is not surprising that accurate cytogenetic diagnosis is also often a challenge, especially when chromosome study reveals morphologic findings that raise the question of normality. Given the realization that modern human cytogenetics is just over five decades old, it is noteworthy that thorough documentation of normal chromosome...