Designer Genes: A New Era in the Evolution of Man by Potter Steven

Author:Potter, Steven [Potter, Steven]
Language: eng
Format: mobi, epub
Publisher: Random House, Inc.
Published: 2010-09-13T16:00:00+00:00

11

MODIFYING GENES

The latest genetic-engineering technology allows us to use stem cells as the starting material to produce individuals with any desired version of a gene. With this approach we can go further than just sorting and selecting from a batch of embryos. Even after examining a large number of embryos the favored gene combination may not be found. In some cases neither parent will carry the sought-after form of a particular gene. With genetic-engineering tools, however, it is possible to take a more active role, and to actually modify genes at will.

In 2007 the Nobel Prize in Medicine or Physiology was awarded to Mario Capecchi, Sir Martin Evans, and Oliver Smithies for the development of this radical new technology. It can be used to accomplish many different types of genetic modifications. It can be used to delete a gene entirely, or to add a new gene that might have been synthesized from scratch in the test tube. Or it can be used to change a gene that is already present in the cell. This change can be major (for example, swapping one large block of DNA sequence for another), or it can be extremely subtle (such as modifying a single base of a gene, perhaps turning a C into an A). This new technology gives us total control over the genetic content of a cell. The genetic-engineering procedures involved are complex, currently requiring months of work in the laboratory to accomplish. It is not as simple as pushing a button. But the results are stunning.

There are three steps. First, the desired version of the gene is made in the test tube. Second, this synthetic gene is introduced into stem cells grown in a plastic dish in an incubator. Third, and perhaps most surprising, a correctly genetically engineered stem cell is used to make a person, carrying the engineered genetic modification in every cell of his or her body. This might sound more like science fiction than science, but these same procedures are routinely used today in research laboratories around the world to genetically modify mice. There is every reason to suppose that this technology would also work for people.

To elaborate: The desired gene changes are created in a test tube using standard molecular-biology techniques. For example, the artificial gene could simply be generated de novo by a DNA-synthesis machine. We just type in the desired base sequence and the machine produces large numbers of the specified DNA molecules. It is possible to synthesize not just single genes, but large collections of genes using such machines. Indeed, the entire genome of a simple bacterium, with all of its many genes, has been machine made. Alternatively, we could take a purified copy of the gene of interest and introduce the desired changes manually, using recombinant-DNA strategies developed in the 1970s. One can purchase enzymes that are used to cut DNA molecules at specific places, and other enzymes for pasting pieces of DNA together. Still other enzyme combinations can be used to change single bases of genes being manipulated in the test tube.

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