If gene therapy to insert a gene and straight Big another helicobacter | There is grandeur in this view of life
Most "genes for disease" is, as we have seen, genetic markers where a variation is statistically associated with a gene that affects the risk of a disease in some mostly unknown, rarely entirely clear, manner. But there are a few, very rare, heritable genetic diseases in which a defective variant of a gene causing concern.
Cystic fibrosis is a known example - a broken jontransportprotein provide all possible nasty effects. Huntington's disease, in which a defective variant of the protein huntingtin accumulates in neurons, is another. When the genetic basis of such a disease is described, it is unfortunately still not always clear what to do with the knowledge. Sometimes it gives the genetic basis a better picture of what the disease is doing - but often the opposite is true, that the disease is better known than the gene, and therefore it is the disease that contributes with information about how the gene works. If the missing protein is normally secreted into the blood, it is possible that with hemophilia or diabetes, to manufacture it and give as a replacement.
But the gene itself can not do anything about, except with gene therapy. Gene therapy is just what it sounds like: trying to cure genetic diseases by giving the patient new genetic material - in the simplest case to carry the gene for the protein that is broken. It's an exciting idea that has been an issue since the seventies. There have been many advances since then, but it is still difficult; it will not be a routine procedure within five years, if we say so.
It is relatively easy to insert genes in bacteria or cells in cell culture. The bacteria has already a system of additional DNA rings, called plasmids, which they carry on, spread to their offspring at the pitch and sometimes even handing out copies to other bacteria. And cells in cell culture can be tricked to temporarily take up DNA molecules by shocking them with an electric field (it is called with a vivid expression electroporation).
But that's not good enough if we want to give a person new genes. Human cells have no system for managing helicobacter and although it is possible to get naked DNA in the body - for example, by shooting (!) Into very small metal balls with DNA on the surface - it will not remain for long. No, for inserting a gene into a human and have it remain there, there is really only one way: we need the help of a virus.
Some types of the virus reproduces itself by inserting copies (called proviruses) of their genetic material into the host cell genome. The most famous is probably retroviruses, where the human immunodeficiency virus HIV is included. (That's why retroviruses requires reverse transcriptase to translate their genome into a sequence that can be inserted into the host cell chromosome and then be expressed as if it were one of the host cell's own genes.)
If we remove all the genes that are not required to infect, copy the genome and insert a provirus, we instead place with the gene we want to bring. The modified viral genome is packaged into a viral particle composed helicobacter of proteins that there would no longer have the recipe. This sterile virus called a vector, helicobacter thus a carrier of genetic material.
This example is of the beta-thalassemia, which provides a form of anemia. The problem here is a lack of beta globin, one of the protein chains that make up hemoglobin, the protein that carries oxygen helicobacter in the blood.
On the one hand, it is a great success, how a patient with beta-thalassemia helicobacter (as in the article called P2) after gene therapy began producing beta globin and could end up with blood transfusions. On the other hand, illustrates the perhaps the biggest difficulty with gene therapy (and why gene regulation is not only a concern for geeks, but actually useful knowledge).
Their vector made up of the beta globin - and a few regulatory sequences. helicobacter It is not enough with a coding DNA sequence to get a working gene; the gene must be expressed in the right place, at the right cell type, too. Before each gene before the coding portion starts, is a region with different regulatory DNA sequences, known as promoter. The promoter is different recognition sequences for DNA-binding proteins, which affects how much gene amortized.
The combination of the regulatory sequences contained in the promoter and the transcription factors that are expressed in the cell determines how much a gene to be expressed. (... Almost. It would not biology if there were more levels than that. We will come to an example shortly!) The beauty of beta globin is that the regulatory sequence is relatively specific, so the expression is limited helicobacter to blood cells.
In addition to the promoter, which is just before the gene, there may be other regions with similar functions helicobacter that are not in the beginning of the gene. They are called
