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Here is the final part of information regarding genetics testing. Again thank you to all
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The genes for celiac disease are widely distributed among the caucasion population -- about 30%.  But less than 1 % of the total population has CD. There are millions of healthy people walking around that have the "genetic markers" the predispose to CD.  A predispostion means that you CAN 
get a disease, but it's not a given.  
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It's my understanding (after being tested by Dr. Fine) that a person needs to have those certain genetic markers in order for it to be possible for that person to develop celiac disease- but just having one or more genetic markers does NOT mean that you have this condition.  In terms of the sibling issue, I've read that the sibling of a person with CD has about a 10-15% chance of also having it.
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Yes, you can have the disease with only one marker. But more to the point, "celiac" is just the tip of the iceberg ... many, many more people develop major health problems from gluten, and don't ever get the classic celiac symptoms at all.  The book "Dangerous Grains" gives a good rundown of the issue (I don't have any financial relation to the book). But basically, if you have any of the genes involved, there is a good likelihood you will react to gluten, or will in the future. Once you react to it, you can't turn off the reaction, and it will affect your health in the long run.
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According to my doctor, Dr. P. Green, all the answers to the genetics of celiac are not known yet. It is believed it is not a simple dominant/recessive trait "thing" that we all learned in school. At this time, genetics cannot be accurately used to diagnose celiac disease and is not an absolute in ruling it out either.  Some genes are known to predispose to celiac but it is believed there are others not identified yet. Symptoms, response to the GF diet and biopsy seem to be the most accurate way to diagnose at the present time.  
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I am no expert, but my understanding is that having any one of the THREE known CD genes means that you have the predisposition to develop CD. You can have the gene and never trigger the CD. You can also respond well to a gf diet even with no CD gene found, though it may well be that many of these cases were not tested by Prometheus laboratories which is the only lab to test for the third gene which they say to date has explained all biopsy-diagnosed CD patients who had previously shown negative for CD genes (because only the two most common markers were looked for).  If you have the gene and no symptoms, I don't know how you know if you are suffering silent symptoms, and it is my understanding that severe, irreversible damage can indeed occur long before any obvious signs of malabsorption - i.e. the villi atrophy to a point of no return, yet no obvious diarrhea, discomfort. So, it would seem the diet a prudent preventive step, though I suppose a regular check-up schedule for antibodies should raise a red flag in time.
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The DQ2 genetic marker is found in over 90% of patients with CD, while it is found in 20-30% of the general population. Similarly, DQ8 is found a smaller but a significant percentage of the general population, but only in 2-10% of patients with celiac disease.  Fewer than 1% of individuals with DQ2 or DQ8 will develop CD, therefore the presence of DQ2 and/or DQ8 alone is not sufficient for a diagnosis of CD. Those who believe that everyone with these markers should go gluten-free (i.e., that 20-30% of the population should be gluten-free),  are in the very small minority, especially among doctors and researchers. This is also the case for many other genetic markers for other diseases. Markers can appear in very large numbers, while the disease only appears in a very small minority of those who have those markers. It makes sense for those with the markers to be more vigilant, but absent any solid scientific evidence that a certain behavior can avoid the disease it does not make sense that everyone with DNA markers for a disorder should drastically modify their lifestyle. Take Care Scott Adams Celiac.com
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Mary in KS
Live well and be healthy

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