“RNA molecules aren’t always faithful reproductions of the genetic instructions contained within DNA, a new study shows. The finding seems to violate a tenet of genetics so fundamental that scientists call it the central dogma: DNA letters encode information, and RNA is made in DNA’s likeness. The RNA then serves as a template to build proteins. But a study of RNA in white blood cells from 27 different people shows that, on average, each person has nearly 4,000 genes in which the RNA copies contain misspellings not found in DNA. ‘It’s unbelievable,’ says Mingyao Li, a geneticist at the University of Pennsylvania Medical School in Philadelphia. Li presented the finding Nov. 3 in Washington, D.C., at the annual meeting of the American Society of Human Genetics.