The appearance and inheritance of the I-cell phenotype in Dictyostelium discoideum

Dictyostelium discoideum, strain NC-4 (haploid) has been found to contain two cell types, termed I cells and R cells, distinguishable by size, flatness, vacuolation, motility, and capacity to initiate centers of aggregation. The present paper has examined the distribution of phenotypes in clones derived from I cells and R cells and has extended the list of differences between them to include differences in genetic stability, nuclear size and number, and modes of cell division. It is suggested that the I cells may be polyploid (perhaps tetraploid) derivatives of the demonstrably haploid R cells.