AUTOMATIC CHROMOSOME ANALYSIS .2. KARYOTYPING OF BANDED HUMAN-CHROMOSOMES USING BAND TRANSITION SEQUENCES

Abstract

Human chromosomes, represented by band transition sequences, chromosome area, centromeric index by area and centromeric index by density, were karyotoyped by computer. A reference set of chromosomes provided frequencies of occurrence of each density class and difference class of the band transition sequence and of each of the 3 global features. The karyotyping program was designed to handle all metaphases, even those from which severely bent and overlapped chromosomes were excluded. In 1 experiment, 21 metaphases were karyotyped on the basis of a reference set and the results were compared with earlier results of visual analysis of band transition profiles developed from band transition sequences: 0.8% errors were made in the visual experiment and 1.4% errors were made in the computer based experiment. In a 2nd experiment, 179 metaphases were divided into reference and test sets and karyotyped by computer with an error rate of 3.4%. By further analysis it was found that metaphases with many misclassified chromosomes could often be automatically distinguished from metaphases with few errors. Thus, by automatic rejection of 7% of the metaphases, the error rate could be reduced to 2.6%. The computer program for chromosome karyotyping will now be implemented in a semi-automatic system for practical clinical chromosome analysis.