Chromosomal characteristic of Chinese hamster cells and their HGPRT-deficient mutant line

Chinese hamster cell line (line K 431, HGPRT+) and its mutant (line K II, HGPRT-) are similar in the numberical composition of the karyotype (modal number 22 chromosomes), but differ in its structureal constitution (occurrence of trisomy, breaks in the centromeric region, chromosome losses and others). Deletion and rearrangement of some heterochromatic segments of the X chromosome appeared with a higher frequency in HGPRT- line and can constitute one of the conceivable causes of the HGPRT activity loss in the mutant line.