New research explains how certain traits can pass down from one generation to the next — at least in plants — without following the accepted rules of genetics. (Credit: © patrick / Fotolia) Enlarge

Mar. 26, 2013 — New research explains how certain traits can pass down from one generation to the next — at least in plants — without following the accepted rules of genetics.

Scientists have shown that an enzyme in corn responsible for reading information from DNA can prompt unexpected changes in gene activity — an example of epigenetics.

Epigenetics refers to modifications in the genome that don't directly affect DNA sequences. Though some evidence has suggested that epigenetic changes can bypass DNA's influence to carry on from one generation to the next, this is the first study to show that this epigenetic heritability can be subject to selective breeding.

Researchers bred 10 generations of corn and found that one particular gene's activity persisted from one generation to the next whether the enzyme was functioning or not — meaning typical genetic behavior was not required for the gene's trait to come through.

And that, the scientists determined, was because the enzyme targets a tiny piece of DNA — previously thought of as "junk DNA" — that had jumped from one area of the genome to another, giving that little fragment power to unexpectedly turn on the gene.

The gene in question affects pigmentation in the corn plant. As a result of these experiments, the researchers were able to change yellow kernel corn to a blue kernel variety by compromising the activity of the enzyme in each male parent.

"This is the first example where somebody has been able to take an epigenetic source of variation and, through selective breeding, move it from an inactive state to an active state," said Jay Hollick, associate professor of molecular genetics at The Ohio State University and lead author of the study. "The gene changes its expression in an epigenetic fashion and it doesn't follow standard inheritance behaviors. Those two factors alone have pretty profound implications not only for breeding but also for evolution."

The study appears online in the journal The Plant Cell.

Plant breeders tend to expect to generate desired traits according to what is known as Mendelian principles of inheritance: Offspring receive one copy of genes from each parental plant, and the characteristics of the alleles, or alternative forms of genes, help predict which traits will show up in the next plant generation.

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