Mutation repair kit described in news@nature, 3 Apr 2005 and ScienceNOW 4 Apr 2005. A team of scientists led by Michael Holmes of Sangamo Biosciences in Richmond, California have developed a method for repairing faulty genes by cutting out the mutated sequence of DNA letters and replacing them with the normal sequence. The scientists used a protein known as “zinc fingers” that attaches to specific sequences of DNA. They engineered the protein to find a known defective sequence of DNA letters. They then bound this “zinc fingers to an enzyme that cuts the DNA molecule at that site”. To repair a damaged gene the enzyme-protein combination is inserted into cells, along with a piece of DNA containing the correct sequence of letters. When the enzyme cuts the DNA the cell immediately tries to repair it and during that process it inserts the piece of normal DNA in the place where the mutated DNA was cut out.
Medical scientists have used the technique to repair a mutation that causes a deadly immune deficiency in T cells (a type of white blood cell) growing in a laboratory culture dish, and hope to be able use it to treat patients with the disease soon. Previous attempts at treating this disease by introducing whole new genes have caused serious problems, including cancer. The reason for the cancer is that the new whole gene did not actually replace the old gene, but inserted itself in a different part of the genome, which seems to disturb the whole cell. The new repair process will avoid that problem as it replaces the damaged gene in the right place.
Editorial Comment: The fact that previous attempts at treating genetic diseases by inserting whole genes into cells has caused problems, is evidence that the whole genome is not a random collection of DNA built up over millions of years of chance and natural processes. It is an integrated whole, with genes designed to interact within it, in a precise and purposeful way. That is why it takes precise, purposeful design and manipulation, as carried out by the John Hopkins scientists, to repair damage done by chance random processes. Nobody rushes out to get a dose of random mutations to speed up their evolution, as the proven result is always disastrous problems such as cancer. (Ref. design, genetics, natural)