Movement of modulator in maize: a test of an hypothesis.

A model of Modulator movement (Greenblatt 1968) from one chromosomal site to another requires that all movements produce potential twin mutations within the affected cell lineage. From this model the prediction would be that (1) untwinned red and untwinned light-variegated sectors within the pericarp of medium-variegated maize must occur in equal frequency even though partners become lost, during ear morphogenesis, to the final pericarp tissue, and that (2) among the backcross progeny of a homozygous P(rr)Mp individual mated with P(wr)/P(wr) pollen, red offspring and light-variegated offspring would occur in equal frequency. Both expectations have been realized and herein reported.