Human gene pool just littered with rubbish

By ANNE BESTON and agencies

Researchers reading the "book of life," as the human genome is known, have made the startling discovery that much of it is rubbish.

The first analysis of the entire set of 3 billion human genetic instructions has revealed far fewer genes than scientists expected.

Only 1.1 per cent of the length of the genome consists of genes and scientists have found our genome is more filled with litter than any completely sequenced so far.

The surprisingly small number of genes means humans have only half as many again as the simple roundworm - 31,780 compared with the worm's 19,099.

Researchers had thought we might have up to 140,000 genes.

But scientists speculate that the junk, known as transposable elements, works in an unknown way to make humans more complex than worms.

Scientists yesterday likened the genome to a household junk drawer. The genes would be the passport and birth certificates stashed inside, but the junk is all the memorabilia that fleshes out who we are.

It means the biological differences that influence everything from our looks to our intellectual ability boil down to just a few thousand key differences, say scientists.

Researchers into human genome have found the instructions are also strikingly similar across all ethnic groups, with every person sharing 99.99 per cent of their genetic code with all others.

All that distinguishes an Inuit (Eskimo) from a Cockney or Aborigine, even Britney Spears from Diana Ross, are variations in 300,000 letters in a 3 billion letter sequence in the human genome.

Last year, researchers said they had cracked the code contained in our genetic material, but yesterday they described what they had begun to read.

Four letters are used in the genetic alphabet.

Each letter is a chemical unit that forms steps within DNA's ladder-like structure.

Variations in the sequence of letters spell out our genes, the instructions to make proteins, the large molecules used to build and operate cells in our body.

Differences between people can come down to between 1000 and 10,000 genetic letters, says Dr Craig Venter, of Celera Genomics, the privately funded group working on the project.

People from different racial groups can be more genetically similar than individuals within the same group.

Scientists have also found that hundreds of human genes appear to have been exchanged with bacteria at some point during evolution.

We also share many genes with more humble organisms - about half with the fruitfly and the nematode worm, and about a fifth with yeast.

Hundreds of genes, containing instructions for proteins, have come directly from bacteria, which partly explains our puzzling ability to metabolise some drugs and alcohol.

Scientists hope the knowledge of how genetically similar we are will encourage social tolerance, but there are potential problems.

Celera scientist Dr Daniel Huson, in New Zealand this week for a biotechnology conference, said his work raised important ethical issues.

"We don't want insurance companies peeking into people's genetic makeup in order to discriminate against them," he said.

" That's one of the biggest worries."

Yesterday, the Government's biotechnology watchdog, the Independent Biotechnology Advisory Council, said New Zealand had to begin tackling the issues.

A public consultation programme will kick off this year and an information booklet will be published.

Said council chairwoman Anne Dickinson: "There is lots of potential for discrimination and it's time we talked about it in New Zealand."

GENE POOL


* Humans have more than 30,000 genes, the tiny thale cress plant has 26,000, the humble roundworm 19,099. Some scientists had expected to find 70,000 to 140,000 human genes.

* The male Y chromosome is tiny and has very few genes.

* A dog is 85 per cent identical to a human in genetic sequence.

* Scientists cracked the code last year, translating the 3.2 billion chemical units in human DNA into letters using A, C, G and T.