A newly cloned gene in corn will help explain how unusual interactions between a parent's genes can have lasting effects in future generations. The finding has implications for breeding better crop plants and unraveling complex genetic diseases.

The new research indicates that an additional molecule, DNA's little cousin RNA, is needed for the intriguing gene interactions known as paramutation. Paramutation does not follow the laws of classical Mendelian genetics.

"Paramutation is this incredibly interesting, tantalizing violation of Mendel's laws," said senior author Vicki Chandler, director of BIO5 Institute at the University of Arizona in Tucson. "It's been known to exist for 50 years, but nobody understood the underlying mechanism."

Classical genetics states that when offspring inherit genes from their parents, the genes function in the children the same way the genes functioned in the parent.

When paramutation occurs, one version of the parent's gene orders the other to act differently in the next generation. The gene functions differently in the offspring, even though its DNA is identical to the parent's version. It happens even when the kids don't inherit the bossy version of the gene. The phenomenon was originally found in corn and has since been found in other organisms, including mammals.

"In previous work, we identified a gene that is absolutely required for paramutation to happen," said Chandler, a UA Regents' professor of plant sciences and of molecular and cellular biology. "Now we've figured out what that gene does, and it's exciting because it suggests a mechanism for how this process works."

Chandler's work is the first to point out that an enzyme known as an RNA-dependent RNA polymerase is needed for paramutation.

Corn, also known as maize, is the most economically important crop plant in the United States. Better understanding of plant genetics will help breeders develop improved strains of crops.

e-mail: cblake@farmpress.com