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Genetic testing: reliability, accuracy, experience?

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Genetic testing: reliability, accuracy, experience?

Postby animus » Sun Apr 14, 2013 4:44 am

I read an article in a magazine before about genetic testing. I thought it would be a good idea for me since I'm adopted and would like to know if I express or carry genes for any kind of condition. Then I can take action early. I was pretty excited about the whole idea until I realized the results may be inaccurate and tell me I have the gene for something when I really don't.

I know how to and have access to gel electrophoresis but I wouldn't know how to isolate genes. I was thinking if I could isolate certain genes then I could separate the sections of DNA and compare it to healthy vs non-healthy sections (I would look this up on the Internet?) and this would tell me whether my gene is "good" or "bad". I don't know if my own testing would be any more accurate but I'd trust it more.

But does the existence of a gene necessarily have to lead to expression of it? I read a book last year that emphasized "genes do NOT cause disease" but I don't quite remember what the author said DID cause disease. Hah! Probably some sort of interaction between steroid hormones and their respective genes they activate...which doesn't help me here.

Has anyone had any experience with genetic testing? Any information anyone would like to share?
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Postby Darby » Mon Apr 15, 2013 1:23 am

You'd need to do PCR with the right primers first. And not every allele has reliable primers...
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Postby biohazard » Mon Apr 15, 2013 8:55 am

It is not "the genes" that cause genetic diseases, since most of us contain all the same genes. It's the certain alleles of these genes that cause, or much more typically, predispose to certain medical conditions. Also, it is worth mentioning that, for example, a gene "for" type I diabetes still only increases your risk to get diabetes, and even with one of the risk alleles the chances to get the diseases is typically something like a percent or two. Not to mention that the very same allele may also have some beneficial effect.

Certain diseases are very straightforward, though. For example, the Duchenne muscular dystrophy requires just a single mutation in one of the alleles of a gene for dystrophin in the X chromosome, and if you inherit this mutation and happen to be a male, the disease always ensues.

Well-known medical/molecular biology companies can perform these kind of DNA tests much more reliably than a lone molecular biologist would do, since they have established protocols for quality control, standardized equipment and reagents, and long tradition in making these tests. They have a degree of inaccuracy like all scientific methods do, but unless you are a competent biologist with up to date instruments and reagents and protocols, I'm certain their inaccuracy is far less than what would be if you tested your DNA yourself. It is also worth remembering that some sources of inaccuracy in DNA testing cannot be eliminated: it is always possible, though unlikely, that you have a disease-causing mutation that is not previously known and thus there are no suitable probes and primers for it at all.

Furthermore, to get any useful information (especially if doing the testing yourself), you need extensive knowledge about the disease-predisposing genes, the types of mutations they most commonly have and their effects. You simply could not screen yourself for all genetic diseases. So you should run a panel of DNA tests for the most common genetic diseases concerning your ethnic background and any tests that would seem appropriate taken family history into account (in your case, this would require knowledge about your biological parents' background).

The genes and their expression is often a very complicated process involving many regulation steps and lots of interaction with other genes, so the existence of a bad allele does not necessarily mean you ever get the disease (for example, many genes may only have one "bad" copy in you and the other, properly functioning allele will prevent the disease). In some cases, though, a bad copy will always lead to a disease, so I'm not quite sure what that book you mentioned tries to say.
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Postby animus » Mon Apr 15, 2013 10:47 pm

Thanks, both of you.

biohazard, that was an excellent answer. Thanks so much for taking the time to write it and share that information with me! If only there were more people with knowledgeable answers like that on Internet forums. We'd all have a lot more of our questions answered. Haha.

Anyway, I think I will have to accept that there's always a chance for error and performing this sort of testing is way out of my skill set and a company would produce much more reliable results. I think I'll try the test, and if there is anything that concerns me, I'll get another one done and hope the same mistake wasn't made twice. Heh.
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