Identification of chick chromosomes in cell hybrids formed between chick erythrocytes and adenine-requiring mutants of Chinese hamster cells.

When chick erythrocytes were fused with adenine-requiring mutants of Chinese hamster cells of two different complementation classes and grown in adenine-free medium for 1 week or longer, mitotic cells were observed containing both chick and Chinese hamster metaphase chromosomes within a single cell. Stable hybrid clones were subsequently isolated that possessed, in addition to a complete Chinese hamster genome, a single specific chick chromosome. Hybrids resulting from fusions involving different adenine mutants retained different, identifiable chick chromosomes. Thus, the two chick genes for the endogenous synthesis of adenine were assigned to the respective chick chromosomes.