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Gene junction

A designer bacterium containing a particular human gene already produces a purified protein product that diabetics use for their injections, writes Prakash Chandra.

india Updated: Oct 21, 2007 22:06 IST
Prakash Chandra

What is the smallest number of instructions coded in the DNA, or genes, that tells cells the proteins to make for sustaining life? The Minimal Genome Project aims to find this out so scientists can create nature’s most ingenious product — living organisms — from scratch in the lab. In the late 1990s, researchers from the Craig Venter Institute for Genomic Research in Maryland discovered the minimum essential genes of Mycoplasma genitalium, a harmless bacterium living in the human genital tract and lungs. By disrupting its genes one by one, they identified 381 genes as indispensable for the organism.

Last month, the team packed these essential genes on an artificial chromosome (the structure that holds genes in place in the cell nucleus). The idea is to insert this chromosome into the nucleus of an M. genitalium cell, whose genetic material has been removed. Once the new genetic material takes control of the cell, a man-made microbe that never existed in nature before is born! It will divide and produce a new generation of cells that contain the man-made genetic instructions. These engineered microbes could be used to manufacture drug compounds like new antibiotics, and to mop up greenhouse gases, radioactive waste, and oil spills. They could even be a source of renewable energy, splitting water into oxygen and hydrogen — a cheap source of ‘green’ fuel. A designer bacterium containing a particular human gene already produces a purified protein product that diabetics use for their injections.

However, synthesising long segments of nucleic acid — DNA and its chemical cousin RNA — is very difficult. The RNA code of a tiny virus like polio, for instance, stretches 7,000 letters long. This becomes millions of letters long with a bacterium genome, and would require another leap in technology altogether. Most viruses are just strands of RNA with a few proteins attached. Bacteria have complex cellular machinery that act on the instruction of genes. Building this used to be science fiction. But not any more, the way the Craig Venter team has midwifed artificial life in pots of chemicals in the lab.