Re: Hereditary Diseases

Don Moody wrote:
It's on my conscience that I did not reply to ukharassedmum, and I don't want my conscience troubled for however long it is going to take, if ever, to clear the clag from inside my one good eye. In view of the replies she got, it is obvious there is a lot of misunderstanding about the topic. I'll try to put it straight.

Most of us would have first heard of genetics at school and in terms of Mendel and his laws, and using words like 'dominant' and 'recessive'. What we learned was in fact only a rough approximation and a confession of ignorance. If Mendel's own results are looked at very closely, they do NOT QUITE comply with his laws! And words like dominant and recessive are only statements that we don't know how genes work.

this is the essence of old fashioned scientific method
hypothesis them proof then a natural "law"

later a counter hypothesis and if proven revision of the law

to day a better model is a many dimensional tapestry constantly being trimmed and rewoven at the edges

The technology to make an Edison photograph was available in Mozart's time but the concept of sound waves was not found until a soot coated glass plate was dropped past a vibrating tuning fork


It is not always true that have gene = have disease. In the first place many diseases depend on more than one gene and on environmental triggers. In the second place many named diseases are not single diseases but terms for a whole bundle of different diseases which have some symptoms in common. Diabetes and cancer happen to be two well-known examples of such packaged diseases. That is why, for example. there never will be A 'cure for cancer' regardless of the bull*** written by fundraisers and publicists. What may cure one kind of cancer may have no effect at all on another kind. There is also the problem that the body will sometimes cure itself. It isn't too fanciful to regard the menstrual cycle in women as a process of getting cancer and curing cancer once a month unless pregnancy intervenes.

So it all begins to look complicated? You aint even started yet, folks. Who actually had what in the past? Look up death certs? You must be joking. We've been over it time and again but I'll illustrate with my grandfather, who died in the early 1930's. That was the pre-antibiotic era and meningococcal meningitis was fatal. His death cert says so. Even if a sharp-eyed doctor had noticed he went down unusually fast, it would have been shrugged off with some sophism like 'he was in a weak condition when he got the infection'. Dead is dead, and a busy doctor has nothing to gain by doing intense studies on a corpse when living people urgently need his attention. From the point of view of hereditary diseases, Grandpa's meningitis is irrelevant. It isn't inheritable. However if his life and behaviour prior to death are explored there emerges the classic picture of undiagnosed Type II diabetes. And that is inheritable as I know to my cost. That explains the fast knockdown. Any bacterium landing in his blood would have reacted as a starving man to a royal banquet. So much freebie glucose to live on. There would have been explosive growth, and that means an explosive rush of toxins. So the first bacterium which got there would have killed him. It was a mere chance that it was a meningococcus. His death cert is useless as an item in the study of hereditary diseases. Ten years later people were stepping in front of bullets or having bombs dropped on their it heads. All those death certs are useless too.

Then there is another problem. The perennial question of 'what is the modern equivalent of X in a death cert of a century or more ago' is a nonsense. We know more now than we did then. So there are new words to sort out what was lumped together then. Furthermore, the hereditable diseases with a payback in old age wouldn't have been much in evidence in a population with a life expectancy of around 40. The classic case is a tribe of the Sioux, n whom there was no evidence of diabetes when they were enduring intense cold, fighting wars, and generlly having a hard life. A Sioux brave in that tribd who reached 40 was an old man. Now? They all live to 70 and there is a 100% incidence of diabetes. In terms of human lifetimes, no there is no easy 'computerised' way of feeding in old data and out pops an accurate assessment of hereditary disease.

Then there are the diseases which look genetic but are not. Much of glaucoma fits this bill. In the peak locations for incidence of glaucoma the common factor is diet. Humans are ingesting directly or through the milk of their cows continuous small traces of an alkaloid called sanguinarine. It occurs in all members of the Papaver and Fumaria familes. Enjoy your poppy-seeded rolls if you want to go blind, and when you do then don't blame your genetics. But there is also a genetic component in some glaucoma.

Now we come to the fact that it is possible to have genes for a disease, not have the disease, but pass those genes to a descendant who does have the disease. My grandather's daughter who became my mother did not exhibit diabetes. Maybe she was too busy dying of lung bance for it to be noticed. But I got my diabetes from her. Similarly, both my male cousin and I carry the breast cance genes from our mutual grandmother. but neither of us have BC. On the other hand we both have daughters who do.

And that leads on to how and why genes get switched on or off. Nobody knows for sure. The problem ecists in your own body. Whether it is a nerve cell in your brain, a liver cell, or a skin cell on your big toe, it has the SAME genes. But those clls neither look the same nor perform the same. Why? All the necessary genes are there. So it isn't just have gene - have result.

Nor is that the end of the complications. Inheritance is a statistical thing. You can't predict which genes you get from Dad and which from Mum. They come across in clumps but it doesn't have to follow that the breakdown into clumps is always the same. A lot can go wrong, and does so more frequently than is realised. The process of getting rid of a high proportion of the mistakes is called miscarriage. Since 'misses' are not recorded there can be no historic information about what genetic liabilities they indicate. And as I have said so often, whereas stats about a population may give information anout inheritability, or otherwsie, of disease, they are of absolutely no use in making deductions or predictions about single cases.

In disentangling a field as complex as this there is no point in expecting to sort it all in 50 plain words in Wikipedia. It needs a whole new language of precisely defined terms in order to have an intelligent discussion of the subtleties and complexities. A language which takes years of intensive study to learn and become fluent. There is no shortuct and no simple translator. Those who want to see what is involved could do what ukharassedmum coyuld have done but evidently did not do before she posted. Enter into Google search "Tourette's +genetics" (without the quotes).. In the first page or two will be a learned paper from a Harvard doctor. Try reading it. Papers written like that are either by pretentious prats concealing their ignorance, or by very solid and knowledgeable folk trying to put forward precisely what they have found. Prats generally do not get through the refereeing process in respectable journals. they publish where there is no check.

In summary, if you want to get involved in genealogy as a poor, but the only available, approximation to genetics in the study of disease in humans, you have a binary choice. Give up and don't bother at all. Or pay your dues with the equivalent of years of full-time study. It is far too confusing for well-meaning amateurs.

In practical terms, ukharassedmum or anybody else in a like state about something serious which their chld may have inherited, has a simple course of action. Get their GP to refer them to a clinical geneticist. Put beffore that geneticist the facts you have found, answer his further question, and then sit back and let the oracle speak from the benefit of 20 years or more of study.

Don

(This took more than three hours to type so I'm afraid there is no prospect of me engaging in continued debate. If anybody is sufficiently disturbed they are welcome to ring me .My phone remains 01626 821725. I am out a lot for hospital visits and treatments. but it is a home number so I'm available at reasonable times outside office hours. You can have the benefit of what is between my ears but I CANNOT make any documentary references. I simply cannot read the documents.)


likewise when "telephone time" came Edison was the lucky winner of the patents out of more than seventy applications

Today we are in gene-technology space and we all have to learn to live with it

I try and follow scientific developments as a fan just like any football supporter - I better get to a library and read some Scientific American back issues - the magazine is written for readers who think well but are not experts in the field of a particular article

good luck Don


Hugh W
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