Mutable loci in maize.

B. McClintock,  Carnegie Inst. Washington Year Book,  47:155-169. 1948.

Previous reports have state that the number of unstable loci have recently arisen in maize culture. In a particular cell of a plant, a normal “wild-type” locus becomes altered; the normal, dominant expression of this locus changes and gives rise to a recessive expression (or, in several cases, a recessive locus become unstable and mutates toward a dominant expression). This expression of the locus need not be permanent. In some decendent cells, a second change may occur within the locus that results in the restoring of the capacity of thelocus to express the dominant phenotype or brings about an intermediate expression between full recessive and full dominant. In the latter case, a third alteration may occur in some decendent cells that steps up the phenotype expression toward the full dominant or reduces it toward the full recessive.