How do scientists change a persons DNA?

Providing it can be changed. I often read about conditions that are a result of a certain gene that can cause it. Today I read that Prostate cancer can be caused by a dodgy gene, and was wondering if they can remove that gene to reduce the risk. If so, how do they go about it?

OK thanks, I’m right up to date with it all now.:dubious:

They can’t really change your DNA (except in the very limited sense that Terr’s link is talking about), not at our current levels of technology, or any that are likely to appear in the foreseeable future. Knowing how certain genes cause, or predispose people towards, certain diseases, however, can still be very useful. For instance, if it is known that you carry a gene that predisposes you toward prostate cancer (or whatever) there might be other measures that can be taken to make it less likely that you will actually come down with the disease, measures that someone without the defective gene might be best not to take, for various reasons (expense, side effects, etc.).

Knowing that potential parents have certain defective genes can also be useful in helping them avoid having children with severe genetic disabilities. If each parent carries a copy of a defective gene, the parents might be OK, but a child who got a double dose of the gene could be in serious trouble. It might be wise for that couple not to have children at all, or else it might be a good idea to have them do in vitro fertilization, and then check any embryos they produce very carefully for defects so that only good ones are allowed to implant and develop.

There is also the possibility that defects in the DNA might be correctable in the sperm or ovum cells before doing in vitro fertilization, so certain defects are not passed on to children. I think a little of this has been done in an experimental way already, and it is not beyond the bounds of possibility that it might become fairly routine before too long. Certainly it is a much more attainable goal than changing the DNA in a whole human body (or even whole organs, or whatever), which really is not on the cards at present, and very likely never will be.

Thanks, that seems to clear up my question. Nice to know they can still do something positive after discovering a dodgy gene.

While we’ve come a along way since the first experimental gene therapies in the 1990s, there are no gene therapies available to remove genes that might cause a risk, but have not developed an actual disease in the patient.

Gene therapies for cancer that has already grown - patients with leukemia or myeloma, or for people infected with HIV, or congential genetic disorders, exist, and are in various stages of experimentation or clinical use. It’s not far-fetched to think that in the near future, adjustment or removal of genes that carry certain cancer risks would be a standard course of action, but that is not the case right now.

So, no, they can’t, for example, remove the BRCA1 or BRCA2 gene (famous for their association with breast cancer, but also associated with prostate cancer.)

You might do better controlling your diet, getting regular screening for prostate cancer, and improving your general health for the moment since any gene therapy for this is in the future.

Also, even for genes that gene therapy exists for, no one has solved various problems of cost, having the gene therapy reach large parts/most of the cell genomes in the patient’s body, immune responses to the therapy, induced tumors, and short-lived effects. Gene therapy is still very young, and may not be appropriate for many patients, although it will probably become much more common in the future.

I don’t know enough about to even attempt to explain it, but a stem cell transplant can pretty much entirely replace a person’s DNA with that of another person.

My brother has been battling leukemia for over two years; it kept coming back after chemo. This spring I was the donor for a stem cell transplant. Last week his doctor told him his DNA is now 97% mine; I don’t understand what that means – he says it means he is going to get a bald spot and become a computer wiz.

Turble: Any tissues which developed from the transplanted cells might be 97% you. Any tissues your brother already had, which were not removed or replaced, are still your brother :slight_smile:

The thing about leukemia is that it is a cancer of the white blood cells that are continually being renewed by stem cells in the marrow. If you can remover the marrow and replace it with healthy marrow–and if you avoid graft vs. host disease which means your marrow attacking your brother’s cells–then you can change his blood entirely. But this does not change the DNA in any other body cell.

Prostate tissue and breast tissue (and all other solid tissue) is not continually replaced in this way and this kind of therapy is not available. You could get a prophylatic (in both senses, I guess) prostatectomy and you could be extra careful about prostate examinations, but I don’t see any possibility of gene therapy for it.

That is not how stem cell transplants work (here’s a short explanation of how they do work.)

As Hari Seldon mentioned, replacing bone marrow stem cells will replace blood cells, but won’t replace brain cells, bone cells, muscle cells, sperm, etc.

Like I said, I don’t understand this stuff and I don’t know what it means when his doctors tell him his DNA is now 97% mine; that percentage has been rising on every test since the transplant and they say it will reach 100%.

The subject is far too complex for me to want to expend the effort to learn about it. I presented the anecdote in response to the OP only as “a” way scientists change a person’s DNA – strictly a FWIW thing.

Continuing the anecdote: The doctor told my brother’s wife “I hope you like Turble because your husband is going to become him.” Surely a joke, of sorts, I know.

It does seem to me that only the blood cells would change. I accept that I don’t understand it.

A common way of tracking the success of a bone marrow transplant is to periodically take blood (or bone marrow) samples, sequence the DNA of that blood or marrow, and measure how much of it came from the donor, and how much from the recipient. As the donor marrow takes over and begins to successfully replicate, more and more of the DNA should be from the donor. But the rest of the body’s DNA remains untouched.

And of course, sibling marrow donors are favored in the first place precisely because you already have very similar genetics, and hence similar immune factors.

Gene therapy can’t now (and probably will never) be able to remove a gene and replace it with a good one. Short of some really impressive nanotech, that’s not a feasible goal.

However, you can insert new genes. If a cancer is caused by a broken gene, inserting a functional one might prevent the problem. For example, some people at a high risk of cancer have a broken gene that triggers cell death when there are mutations; without that cell death, it’s more likely that a cancerous mutation thrives and becomes a tumor. It’s theoretically possible, then to insert the working version of the gene and maybe prevent this problem. (Of course, using that as the example, this would mostly be useful before cancer occurs, not after.)

Even when you insert a gene, usually you wind up with both the broken and good one working at once. The broken one is maybe producing a nonfunctional protein, so having a functional protein from the good one could be all you need. But if the bad gene is directly producing a bad result, well, just having it left behind could be a problem in and of itself.

Actually, technologies like CRISPR and RNAi make it somewhat feasible to get the same effect.

What effect, exactly, are you talking about, and how do these technologies achieve it? Are they equivalent to the removal or replacement of a defective gene in all the relevant cells of a person’s body? That that seems to be what the OP was talking about, and I think dracoi is right, it can’t be done and won’t be done in the foreseeable future, if ever. If you are talking about dosing people with bits of extra-nuclear nucleic acid that will lead their cells to produce some protein that they are missing, that is really a very different matter.

The bio lab I work for is currently working on a technique to remove specified segments of DNA from any cells the viral delivery agent can infect. The first test is removing HIV proviral DNA from HIV-infected cells.

I thought about mentioning CRISPR, also.

I’m not all that familiar with CRISPR, but it may be promising. As Wikipedia mentions, they need to figure out some things like delivering it to target cells and only the targeted regions.

Anybody more familiar with this?

CRISPR has the potential to remove or even replace defective genes. Of course, the difficulty is as it’s always been - getting the machinery into the cells you want to affect, so changing the entire body’s DNA is still entirely impractical. But CRISPR is more powerful than just the “adding in some extra DNA” that we’ve been able to do for a while. Briefly, CRISPR is a technique that allows you to cut the genomic DNA exactly where you want to cut it. You can guide it to one specific base out of the entire genome. That may not sound terribly impressive, but you can then exploit the cell’s natural repair systems, which kick in after the cut is made.

You can do things like cut in two places and remove the intervening sequence. If you also inject some properly engineered replacement DNA, you can, with some luck, get the cell to pop your desired DNA sequence in where the gap was.

In fruit flies, it’s just ridiculous what you can do with it, when you combine it with other well-established techniques. You can pop out any specific gene (in specific tissues at specific times, all completely under your control) and replace it with a mutant version. And then later, remove the mutation and replace it with yet another version.

So in theory, say if you were wanting to treat cystic fibrosis, you could (if you could infect the lung epithelial cells properly) not only supplement the cells with an extra functional copy of the CFTR gene, which has been tried before, but you could get more precise. With the right CRISPR machinery, you could quite easily go in and actually fix the mutation in the cell’s own genomic copies of the gene. There are still, obviously, massive technical hurdles, but the technology is there.

Labs are also playing with using different virus vectors to deliver the CRISPR/CAS9 system to cells. Viral vectors can be engineered to infect only cells with a particular receptor…which can increase specificity. Of course viruses are a very good tool, at least currently, to get genetic material into cells.