Genes and the genetic research problem

When I studied genetics, back in the 1970s it was all about fruit flies and sweet peas. This was because once you moved away from single gene variations, problems became exponentially difficult. And even with a single gene variant, there was a question of whether the gene expression was dominant or recessive. If a gene was dominant only one gene of the pair needed to be altered for the gene to have consequences, whereas if it was recessive both copies of the gene needed to be altered. Genes come in pairs, one from the father and the other from the mother) So now scientists have mapped the human genome (1990-2003). We have 46 chromosomes, 23 pairs. Each chromosome contains thousands of genes. There are about 20,000 genes coding for proteins. There are 3 billion odd base pairs. Finding which gene is connected to psoriasis might have been a reasonably simple task if there had proved (among even all of this) to be a single gene causing the disease, dominant or recessive. But years of research has in fact shown that the situation is very complex. This information I got from the US National Psoriasis Association. From 2006 they collected samples of DNA from psoriasis sufferers, and since 2010 they have been releasing them to researchers. The scientists have now identified 25 GENETIC VARIANTS that make a person more likely to develop psoriatic disease. Studies have shown several genetic areas where more than one gene may be involved. Research is ongoing as to which types of psoriasis are involved with which genes. There are, then, problems because of the multiplicity of genes. How many of the variants do you need? What combinations produce a result? How does the dominant-recessive question affect expression of the disease? I am not much of a mathematician, so I will not even try to calculate the number of variations from 25 genes mixed and matched in combinations from 1 to the whole 25. On top of that, the National Psoriasis Association says that at least 10% of the general population (in the USA?) inherits one or more of the predisposition genes, but only 1% to 2% of the population develops the disease. So now you might see that even 16 years after the genome project finished, research has still not found the cause, and has still not found the cure. In fact I suspect that psoriasis and psoriatic arthritis may prove to be a bunch of different things. After all there are a bunch of different triggers, and a bunch of different treatments that are effective for some and not for others. There may be a bunch of causes, and a few different cures. A lot of effort is going into all this research. Eventually there will be positive results. But like the research into cancer, it is likely that there will be different and variably effective answers. At 72 I think any answers will be a bit too late for me. wendyloish