Ethics Of Dna Testing For Inherited Disease

The applications of recombinant DNA technology are exciting and far-reaching. However, the ability to examine the base sequence of an individual raises important ethical questions. Would you want to know that you had inherited a gene that will cause you to die prematurely? Some of you might feel fine about this and decide to live life to the full. We suspect most people would not want to know their fate. But what if you have no choice and DNA testing becomes obligatory should you wish to take out life insurance? In the United Kingdom insurance companies are now able to ask for the results of the test for Huntington's disease. This is a fatal degenerative brain disorder that strikes people in their forties. From the insurance company's point of view DNA testing could mean higher premiums according to life expectancy or at worst refusal of insurance cover. There is much ongoing debate on this issue.

On the positive side, we can now test for changes in certain genes that are involved in drug metabolism. Adverse drug reactions are the fourth highest cause of death in the United States. By knowing, for example, which individuals carry mutations in genes coding for cytochromes P450 (page 249), medicines that need to be metabolized by these proteins can be avoided.

Analysis of fetal DNA can inform parents if their child is affected by an inherited disorder. It is now possible, using the PCR, to examine the genotype of a single cell from an eight-cell embryo. If the DNA test is negative, the embryo can be inserted into the mother, and the parents know they have not passed on a defective gene to their child. This combination of DNA testing and in vitro fertilization has given rise to the unfortunate phrase "designer babies".

In the future it may be possible to correct genetic defects before or after birth by replacing mutated genes by a normal copy. The technology to carry out such experiments is very demanding and important ethical questions are raised. In Chapter 20 we will discuss the potential use of gene therapy for the correction of the genetic disorder cystic fibrosis.

IN DEPTH 7.1 Genetically Modified (GM) Plants—Can They Help to Feed the World?_

The arguments about the value of GM crops and the damage they cause the environment will continue for a long time. These have largely concerned plants that produce insecticide and plants that are resistant to herbicide. Almost unnoticed in the maelstrom of claim and counterclaim has been the use of genetic engineering to produce nutritionally enhanced crops. Rice is a staple food in many countries but lacks many vital nutrients. About 800 million children suffer from vitamin A deficiency, which can result in blindness and a weakened immune system. In an attempt to overcome this severe nutritional deficiency, a group of Swiss scientists have engineered the rice endosperm to produce provitamin A (beta-carotene). This is converted in the body to vitamin A. Four genes were introduced into the rice endosperm, three genes from the daffodil and one from the bacterium Erwinia. These genes code for all the proteins needed to make beta-carotene. The transgenic rice is golden in color because of the presence of large amounts of beta-carotene.

Almost 24% of the world's population, mainly women, are deficient in iron. Rice has been engineered with the gene for ferritin, an iron-binding protein. This rice has higher amounts of iron and has been shown to correct iron deficiency in laboratory animals. The plan is to cross the provitamin-A-enriched, iron-enriched strains with agricultural rice strains to produce a hardy and nutritional crop. Golden rice, enriched in iron, provides a great opportunity to improve the health of billions of people.

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