HERITABLE CHANGES IN R-LOCUS EXPRESSION IN MAIZE IN RESPONSE TO ENVIRONMENT

Abstract

is a basic assumption in genetics that hereditary units cannot be altered from ‘:en eration to generation by means of environment. This assumption has resisted serious experiniental questioning for the past 50 years because one or more critical components has always been lacking in experimental designs. With the availability of the paramutational system, it has become possible, in maize inbreds, to inquire whether heritable environmental effects can be assayed in the pigment expression of a single gene. Operationally, the gene is known through its expression, the phenotype; heritable phenotypic changes, regardless of how these changes are caused, will be an argument for a change in the gene. BRINK (1956) reported in studies of the R locus in maize that the R allele, responsible for kernel color, could be changed in its ability to produce pigment by possing the R gene thrcugh a heterozygote with its allele Rat (stippled). When R is removed from the ,TiRSt combination, less pigment is noted in the following generations. The effect is called paramutation by BRINK. The significance of the paramutation phenomenon to the work presented here is that (1) a change has been directed at a specific gene. (2) the change occurs in a high frequencyloo%, and (3) the change in R expression is heritable (found in all offspring with R) .