Description of chromosome banding patterns by band transition sequences: a new basis for automated chromosome analysis.

For visual and automated analysis of banded human chromosomes, the band pattern features of chromosome profiles considered essential for the cytogeneticist were evaluated. These features were found to be related to each peak (dark band) and its adjacent valley (light band) in the direction p--q. A method for extracting and describing these features was developed and implemented on a computer. The method determines three normalized parameters for each peak and adjacent valley: (1) density of peak; (2) density difference (transition) between peak and valley; and (3) position of peak. Each profile is described by a simple sequence of band transitions (BT-sequence). The BT-sequence was visualized as a profile (BT-profile) using only the information retained in the BT-sequence. Visual classification of BT-profiles shows error rates comparable to visual classification of ordinary density profiles (Lundsteen & Granum 1979). It is therefore concluded that the BT-profiles do retain the important band pattern features of the profiles, and it is supposed that the simple and condensed BT-sequences constitute an appropriate basis for automated karyotyping.