The Italian Almanac
Italian Science - September 6
Sections of DNA formerly dismissed as junk contain information vital to our genes, a team of Italian researchers has discovered. Introns, which account for around 25% of the human DNA sequence, play a role in embryonic development and in important cellular processes, according to a study by scientists from the IRCCS Medea Institute near the northern town of Lecco.
The report, to be published in the scientific journals Human Molecular Genetics and Trend Genetics, overturns the long-held belief that introns are "junk" sequences, evolutionary artefacts from the past that have outlived their usefulness. "We found that far from representing junk, they contain information that is important for the functioning of our 30,000 genes," said one of the study's authors, Uberto Pozzoli.
"It is not so much the number of our genes but how their functions are regulated that makes humans humans, mice mice and worms worms. While this was already understood, it was far from clear that introns also helped make us human." Since their discovery in the late 1970s, introns have been dismissed as useless. Their location scattered along vital protein-coding sequences known as extrons, which account for less than 2% of human DNA, left scientists baffled.
But the full DNA mapping of other organisms - dogs, chimps, mice, pufferfish - has allowed an extensive comparison with human DNA, leading to a scientific re-evaluation of the intron's purpose. Taking this discovery as its starting point, the Italian team proved that the location of introns in the DNA sequence suggests they play a role in the correct formation of messenger RNA, molecules that act as "blueprints" for protein synthesis.