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Posted on 04/19/2011 12:03:55 AM PDT by neverdem
If inherited genes are not to blame for our most common illnesses, how can we find out what is?
Since the human genome was sequenced, over 10 years ago, hardly a week has gone by without some new genetic "breakthrough" being reported. Last week five new "genes for Alzheimer's disease" generated sometimes front-page coverage across the globe. But take a closer look and the reality is very different.
Among all the genetic findings for common illnesses, such as heart disease, cancer and mental illnesses, only a handful are of genuine significance for human health. Faulty genes rarely cause, or even mildly predispose us, to disease, and as a consequence the science of human genetics is in deep crisis.
The human genome sequencing project was based on a huge, but calculated, gamble. The then leaders-to-be of the project believed that faulty genes inherited from our parents were probably the cause of most disease. After all, many rarer diseases were already known to be genetic. So it seemed a small leap to suppose that inherited faulty genes would underlie common diseases, too.
There was, however, a problem with the basis for their confidence. The best scientific evidence in humans for genes as causes of common disease was based on comparing disease rates in genetically identical twins against rates in non-identical twins (who share 50% of their DNA). These comparisons, called heritability studies, aimed to measure the relative contributions of genetic variation versus environmental variation.
Although extremely widely used and cited, these studies were considered worthless by some geneticists. Richard Lewontin of Harvard University, for instance, called in 1974 "for an end to the measurement of useless quantities". Other critics pointed out that these experiments relied on the proposition that identical twins experienced no more identical environments than did non-identical twins, when it...
(Excerpt) Read more at guardian.co.uk ...
Is that an assumption, or has it been proven in humans that's the difference between identical twins and fraternal twins? IIRC, the Human Genome Project in the 1990s was begun before they discovered copy number variation of genes, i.e. non Mendelian genetics, epigenetics, and that the non-coding parts of DNA between the genes in chromosomes that coded for protein, exons, that were not just junk DNA - the introns - which had at least some regulatory functions on the expression of genes making proteins.
Even though many disease are genetic, there is still the fact that a person can be a carrier of the disease but have no obvious signs or symptoms, and that person’s sibling can have a very severe form of the disease and die at a young age. Look at the disease neurofibromatosis for such an example.
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This is simply eugenics. There is a reason why nothing gets done.
In Israel where Tay-Sachs is common they offer free screenings. How it works is once you are in the database you ask if a member of the opposite sex you are interested in is a match for you. If the match might result in the disease you are told so, however you are not told if it was you or the other person who has the gene.
I believe that an important factor that is not being looked at is nutritional genetics. For example, it has been suggested that some Chinese may need only 1/5th the amount of calcium in their diet compared with European types. My mother’s parents came from centuries of large dairy farm owners in Germany. I have an especially high need for calcium. Suffered severely from menstrual cramps and back pain until I started taking an extra 1,000 to 1,500 mg of calcium over and above the quart of milk I normally drank. After menopause, I also discovered that I needed to take extra Boron as well to prevent osteoporosis symptoms. Vitamin C is another nutrient that I need large quantities of to prevent allergies. If they are looking for an allergy gene, rather than a Vitamin C utilization gene, then they won’t find a gene for allergies.
I think that genetic studies of nutritional needs and utilization could be a major new area of study in genetics. In addition, I have noted two distinct physical complexes among my siblings, children and relatives. The dark, slightly swarthy ones, and the blond, light brown hair and fair ones. The dark ones are prone to depression and in some cases heavy drinking. Now it seems that Vitamin D may be useful for symptoms of depression.
... was a raving commie.
Quite true. And which genes are expressed and how can vary due to nutrition, infection, and other environmental factors.
Exactly. Those same studies of twins have shown that as time goes on, the gene expressions are not identical and in fact diverge more and more.
Ain’t so much what you got, as it is what’s turned on!
I have the same issue with chocolate.
Sorry, can't help but note the parallel to global warming bandwagon.
As dr_jew correctly points out, Lewontin was "a raving Commie." Lewontin also claimed not to believe in the genetic heritability of intelligence, aggression, or just about anything else. Among the folks you might call "anti-genetic Commies," such as Lewontin, Levin, and Stephen Jay Gould, the point seems to have been to keep hope alive that man is not inherently a competitive, aggressive creature, and therefore will make a nice sheep to be ruled by the dictatorship of the proletariat when that occurs. You might think I'm exaggerating, but I'm not. They talked this way, warning that if research on the heritability of behavioral tendencies continued, we might never see what they called (in public) "meaningful political change." What a waste of tenure.
We are talking about a clip from The Guardian here. There's actually not much of a story. I'm sure the genome project will prove useful in time. But if we're talking about real science, there's no predicting what theories it will advance or disprove. Cutting the legs off the "junk DNA" theory was huge, in my opinion. It's a big world in there, folks.
Tay-Sachs is an autosomal recessive disease. Meaning that, if you are told that marriage to a particular person will result in 25% of the resulting children having Tay-Sachs, you BOTH have the faulty gene.
That's an assumption based on the fact that each gamete contains 50% of the parent's DNA, selected utterly at random. Although the percentage of shared DNA probably averages out to 50%, the reality is that the shared percentage can range from slightly above 0% to 100%. Without doing a single experiment whatsoever, I would predict that a population analysis of the proportion of shared DNA between siblings would result in a normal (bell-shaped) distribution, with the center around 50%. The extremes of slightly above 0% and 100% are highly unlikely, but not impossible.
The reason I say the shared percentage cannot be 0% is that the children always have their mother's mitochondrial DNA. I'm not sure how much of the genome that represents--less than 1%, but not 0%.
I should also point out that this analysis does not include identical twins or triplets; they have nearly identical DNA.
It’s a little reminiscent of the ‘60’s when many theorized that most cancers had viral etiologies...and vaccines to prevent cancer were just around the corner!
But some microbes have been linked to particular cancers, e.g. human pappilloma virus and cervical cancer in women, Epstein-Barr virus and Burkitt's lymphoma, helicobacter pylori and MALT stomach cancer, IIRC, MALT means mucosa associated lyphoid tissue, etc.
Type 2 diabetes, like type 1, may be an autoimmune disease, researchers say
Scientists develop compound that effectively halts progression of multiple sclerosis (in animals)
Multi-drug resistant staph in 1 of 4 supermarket meat samples
FReepmail me if you want on or off my health and science ping list.
Thanks for the link!
Yeah, but if the expectations were a 10, the reality is a .00000000000000001!
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