Esterase gene expression in Chinese hamster and mouse lymphoma hybrids isolated under nonselective pressure

Hybrids between a fibroblastic Chinese hamster cell line (CH23) and a mouse lymphoma cell line (P388F36) were produced and isolated by a simple new method without using selective media and avoiding contact with the parental cells. The chromosomal situation in the two hybrid types (PCM and PCS) isolated suggested that growth on glass surface (PCM) or in suspension (PCS) depended on the number of hamster and mouse chromosomes which existed in the hybrids. Chromosomal stability in hybrids grown as monolayers (PCM) was reached at a stage in which two to four mouse chromosomes coexisted with no fewer than 19 hamster chromosomes. In a study of gene linkage utilizing clones of this hybrid population, five out of nine genes regulating the synthesis of different esterases in the mouse cells used were found to be unlinked.