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Researchers at University College Dublin have identified a genetic "switch" that determines the sex of cannabis plants, and found the same system may exist in hops. The study, published in New Phytologist , pinpoints a specific section of the X chromosome that influences whether cannabis plants develop as male, female, or both.

"It was known for quite a while that female cannabis plants possess two X chromosomes and male plants carry an X and a Y chromosome, but there are thousands of genes on those chromosomes," said Associate Professor Rainer Melzer, senior author of the study. "Which of those genes determines whether a plant becomes male or female was unknown."

Within a small stretch of DNA, researchers identified three closely linked genes that act together to control both male and female development.…