Computer-Oriented Analysis of Human Chromosomes. I. Photometric Estimation of DNA Content

Abstract

The potential value of DNA content as a parameter for karyotype analysis is presented, and a method is developed based on optical density measurements of gallocyanin-chrome alum stained chromosomes. The optical information is obtained automatically in digital form by CYDAC, a special purpose cytophotometer. A partly automated computer analysis of the data then provides the relative stain content of individual chromosomes and chromosome arms. Experience with three metaphases from the same human female indicates stable clustering of the results, with sufficient discrimination among clusters to identify eleven discrete chromosome classes. It would appear from the values obtained that gallocyanin-chrome alum stain content of individual chromosome arms correlates closely with length and ultraviolet absorbance values given in the literature. It is not yet clear whether stain content represents DNA content alone, or includes other constituents of the chromosome that tend to be proportional to DNA content. Judging from the analysis of errors, improvement in the resolution of the photometric method can be expected. This approach has promising applications in the automation of karyotype analysis and as an additional and powerful parameter in cytogenetic study.