Human Chromosomes: I. Preparation, Analysis and Diagnostic Implications of Abnormalities

This presentation is designed to help persons unfamiliar with cytogenetic terms and techniques to understand how chromosomes are prepared and analyzed to determine if abnormalities exist. A diagrammatic flow-sheet has been used to show how peripheral blood is treated to stimulate growth of cells, and how chromosomes are dispersed and made readily visible. Technical details have been replaced by simple statements explaining the various steps. By careful attention to differences (over-all length, position of centromere, length of arms, presence or absence of satellites), chromosomes may be arranged in order of length and into definite groups to form a typical karyotype of a person's cells. Familiarity with chromosomes makes it possible to determine (a) if an extra chromosome is present, (b) if a chromosome is missing, or (c) if an abnormal chromosome exists.