Scientists: Mapping of complete human genome finally done

Scientists say they have finally assembled the full genetic blueprint for human life, adding the missing pieces to a puzzle nearly completed two decades ago.

An international team described the first-ever sequencing of a complete human genome – the set of instructions to build and sustain a human being – in research published Thursday in the journal Science. The previous effort, celebrated across the world, was incomplete because DNA sequencing technologies of the day weren’t able to read certain parts of it. Even after updates, it was missing about 8% of the genome.

“Some of the genes that make us uniquely human were actually in this dark matter of the genome and they were totally missed,” said Evan Eichler, a University of Washington researcher who participated in the current effort and the original Human Genome Project. “It took 20-plus years, but we finally got it done.” Scientists said this full picture of the genome will give humanity a greater understanding of our evolution and biology while also opening the door to medical discoveries in areas like aging, neurodegenerative conditions, cancer and heart disease. “We’re just broadening our opportunities to understand human disease,” said Karen Miga, an author of one of the six studies published Thursday.

The first draft of the human genome was announced in a White House ceremony in 2000 by leaders of two competing entities: an international publicly funded project led by an agency of the US National Institutes of Health and a private company, Maryland-based Celera Genomics.

The human genome is made up of about 3.1 billion DNA subunits, pairs of chemical bases known by the letters A, C, G and T. Genes are strings of these lettered pairs that contain instructions for making proteins, the building blocks of life. Humans have about 30,000 genes, organised in 23 groups called chromosomes that are found in the nucleus of every cell. To find such genes, scientists needed new ways to read life’s cryptic genetic language.

Reading genes requires cutting the strands of DNA into pieces hundreds to thousands of letters long. Sequencing machines read the letters in each piece and scientists try to put the pieces in the right order. That’s especially tough in areas where letters repeat.