Re: ARE THER ANY ILLNESSES SCIENISTS HAVE FOUND A CURE FOR BY MANIPULATING DNA?

Well, the question is pretty vague so it leaves a lot to interpretation. There are many ways in which we could define "illnesses cured by DNA manipulation". I will try to briefly cover all of them with an example.

Vaccination is one way we can prevent people from aquiring a disease. What we do is give the immune system a piece of protein from a bacteria or virus, or in some cases(polio) the whole virus that the immune system can recognize as foreign, make antibodies and activated T-cells that will search and destroy the actual bacteria or virus if it eventually does infect our body. How do we get this protein? Well, we used to grow up lots and lots of virus or bacteria and kill them by breaking them apart to render them harmless, then taking those proteins that are best able to cause an immune response. Not anymore though. With the technology of recombinant DNA, we have the ability to take a piece of DNA from one source (say a virus), and put it into something else that can use that DNA to make its gene product. For example, we can take a piece of viral DNA that codes for the virus coat(the shell that keeps the virus together and carries the DNA within) and "clone" it into a bacterial piece of DNA called a plasmid. We can then put that plasmid into E. coli, and make the E. coli produce lots of that virus "coat" protein in amounts that we can purify and use for a vaccine. That way we don't have to work with a whole virulent virus everytime we need to make a vaccine.

There are also genetic diseases which are caused by a defect in a protein that is made from our own genes. For example, Sickle Cell Anemia (SCA) is a genetic disease where Sickle Cell Beta-globin( one of the molecules that carries oxygen to the cells) was not made correctly. A gene is a blueprint for making proteins, and the sequence of this gene is very critical. There are 4 bases of DNA: A,G,T, and C. These bases are strung together like letters in a sentence, and the order of the bases give the directions for what amino acids (the building blocks for making proteins)are placed together, and in what order, to make a protein. By changing one base from say a G to a C, we may change the amino acid needed to make a correct protein, for another that results in an incorrect protein.

So what happens in SCA is that an incorrect form of beta-globin is made that has one incorrect amino acid. The 6th amino acid used to make normal beta-globin is glutamate, but in someone who has sickle cell anemia, the number 6 amino acid has been changed to valine. The entire beta-globin protein is 146 amino acids in length, and that one change was enough to cause a fatal disease. What happens is that when the beta-globin protein is not carrying oxygen, this valine residue becomes "sticky" and binds to the other end of the protein. This causes the beta-globin proteins that cover the surface of the red blood cell(RBC) to form strands that squeeze the RBC into a sickle shape. Now the RBC can't fit through capilaries, which prevents surrounding tissue from getting oxygen.

One of the ways we are trying to cure SCA is by using something known as gene therapy. What that entails is delivering a correct copy of the beta-globin gene to the cells that make red blood cells(RBC), so that when RBC's are made, they have the correct form of beta-hemoglobin. There are still many difficulties and problems associated with this type of treatment, so as of now it has not led to a cure for any genetic disease. Bone marrow transplants for SCA are effective in curing this disease.

Other relatively common genetic diseases include Adenosine Deaminase Deficiency (an immune system disorder), some types of cancer, and cystic fibrosis. Right now gene therapy is a very "hot" topic for ethics, and may be something you want to investigate.

The last one I will mention is a disease known as diabetes. You have probably heard or even know someone affected by this disease. Basically people with this disease either produce a defective insulin protein (type 2), or the cells that make this protein are killed by the immune system (type 1). In either case the result is the same. Insulin is a protein responsible for telling cells to take up glucose from the blood stream. Cells use glucose for their main source of nutrition so that they can make energy to perform all their necessary functions.

Since cells are not taking up glucose, the levels in the blood get too high, causing it to be excreted by the kidneys along with lots of water. Dehydration can occur very easily, and can lead to seizures, or even coma. People who have diabetes can administer their own insulin (along with a controlled diet of low sugar) that effectively treats the disease. We used to get the insulin from pigs, but now we can use molecular biology to take a healthy gene for insulin and make bacteria produce lots of insulin for us to purify. In this case a disease isn't cured, but is managed though DNA manipulation.

That should explain each possibility. Sorry it wasn't as brief as I had planned it to be, but the information should provide you with plenty to think about.