Decoding the human genome

WASHINGTON - SCIENTISTS have decoded the three dimensional structure of the human genome, opening the way for new insights into its functioning and structures, according to a report published on Thursday.

'By breaking the genome into millions of pieces, we created a spatial map showing how close different parts are to one another,' said Nynke van Berkum, one of two main authors of the study, which appears in the journal Science. 'We made a fantastic three-dimensional jigsaw puzzle and then, with a computer, solved the puzzle,' said Dr Berkum, a postdoctoral researcher at University of Massachusetts Medical School.

To do it, scientists used a new technology called 'Hi-C' that allowed them to solve previously unanswered questions about how each human cell could contain some three million pairs of base DNA and still be able to access functionally crucial segments.

'We've long known that on a small scale, DNA is a double helix. But if the double helix didn't fold further, the genome in each cell would be two meters long,' said Erez Lieberman-Aiden, a graduate student in the Harvard-MIT Division of Health Science and Technology and a researcher at Harvard and the Broad Institute.

'Scientists have not really understood how the double helix folds to fit into the nucleus of a human cell, which is only about a hundredth of a millimeter in diameter. This new approach enabled us to probe exactly that question,' said Mr Lieberman-Aiden, the study's other main author.

The researchers found that the human genome is organised in two distinct compartments that keep active genes accessible to proteins and separate from densely packed stocks of inactive DNA. Chromosomes snake from one compartment to another as their DNA alternates between active and inactive stretches of the genome. -- AFP