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[IP] Skipping Generations

Laura Arns wrote:
> Perhaps my "skips
> a generation, oldest child" rules are outdated, does anyone know of more
> recent theories on how diabetes is passed on through the genetic chain?

Skipping generations is an old-wives tale!

The genetics for Type 1 and Type 2 are distinct -- they are 2 separate

In Type 1, you must have certain genes that cause you to be susceptible
to auto-immune problems, AND you must encounter whatever pathogen or
toxin (probably a virus) that triggers those genes. 

Therefore, not everyone who carries the genes develops Type 1, and so it
pops up, seemingly at random in families where no one is aware of any
previous history (do you know whether a relative 4 or 5 generations back
mightn't have died of Type 1?? Most people don't!).

However, in families where the gene has become evident, i.e. families
where one member has Type 1, you can test the others and will often find
that others are susceptible, too. Whether they actually ever GET Type 1
is not at all a sure thing, but the susceptibility is there, and can be
inherited by THEIR descendants.

Type 2, on the other hand is MUCH more heritable, and family history is
positive much more often. In fact, endocrinologist James R. Gavin III
said that it NEVER skips generations. However, it may not manifest if
conditions aren't right (or wrong!) -- if someone is constantly
underfed, they may never gain enough weight for Type 2 to show up, and
diagnostic criteria have historically not been sensitive enough to pick
up everyone who actually has it. 

Type 2 in grandparents is NOT a predictor of Type 1 in children -- all 4
grandparents can have Type 2 diabetes without necessarily having any
connection with a child's being diagnosed Type 1. 

However, it has become apparent in very recent years that a certain
percentage of adults who are diagnosed as Type 2, are, in fact,
slow-onset Type 1's; that is to say that their diabetes is auto-immune
in nature, and sometimes grandparents may have that kind of diabetes,
which IS related to Type 1 in children. 

Another thing to watch out for is the fact that a Type 1 CAN have the
genes for Type 2 as well. That means that as the person ages, they can
become obese, and start showing Type 2 insulin-resistance and
hypertension and hyperlipidemia problems. The two forms of diabetes are
NOT mutually exclusive.

OK, more than you ever wanted to know, eh??

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