GRcade

http://www.guardian.co.uk/science/2008/jan/25/genetics.science

The biologist and entrepreneur Craig Venter has announced the creation of a synthetic chromosome, knocking down one of the final hurdles to building the world's first artificial life form.

Venter, best known for his race against publicly funded scientists in the 1990s to sequence the human genome and more recently for hunting the oceans for unknown genes, said the latest work was a "significant but not final step" to creating new life.

In a paper published today in Science, Venter's team described the synthesis of the entire genome of the bacterium Mycoplasma genitalium from laboratory chemicals. The resulting DNA sequence has about 582,000 base pairs of genetic code in 485 genes. Venter said it was the largest artificial sequence ever made, 20 times longer than any previous attempt.

The team at the J Craig Venter Institute (JCVI) in Maryland is working on the final step to create life: transplanting the synthetic DNA into a cell in the hope that it will "boot up" the cell and take control of its growth and reproduction.

The scientists, led by Nobel laureate Hamilton Smith, began by building long strands of DNA, each a copy of about a quarter of the whole M genitalium genome. These were inserted into yeast cells, which stitched together the strands to make clones of the whole genome, named M genitalium JCVI-1.0.

The next step is to insert the synthetic chromosome into a cell, so that it can reproduce and become a new life form. Venter's team has already demonstrated that transplanting the genome of one type of bacterium into the cell of another can change the cell's species, a process his team will now use with the new synthetic chromosome.

Smith said that producing the artificial genome was like finishing the operating system of a computer. "By itself, it doesn't do anything, but when you install it on a computer, then you have a working computer system. It's the same with the genome: the genome is the operating system for a cell and the cytoplasm is the hardware that's required to run that genome."

The work comes out of a larger JCVI effort to discover the minimum number of genes needed for a life form. In its natural state, M genitalium has 485 genes, 100 of which have been found to be non-essential. Synthetic biologists want to use this information to create the most efficient form of life possible, with the fewest genes needed to allow the organism to grow, replicate and proliferate.

Venter said there were two main reasons for the work. "One is trying to understand the minimal operating system of a cell and to understand basic biology. If these experiments are successful we could enter a new design phase of biology by actually constructing chromosomes of a specific nature for a more specific purpose."

Stripped-down designer organisms have huge potential for creating alternative sources of energy or tackling climate change by soaking up carbon dioxide.

Venter has previously claimed that an artificial fuel-producing microbe could be the first billion- or trillion-dollar organism. "When you think of all the things that are made from oil or in the chemical industry, if in the future we could find cells to replace most of those processes, the ideal way would be to do it by direct design."

But Jim Thomas, of the Canadian bioethics organisation ETC group, called for a moratorium. "In the absence of democratic oversight profiteering industrialists are tinkering with the building blocks of life for their own private gain."