Re: another genetic question!

[Guest guest]

>

>

> I think I'm probably addressing this question to Philip D., who

> appears to be very well versed in genetics! Thank you for you

> response to my first question. I must admit that I didn't

> understand all of the specifics, but I get the jist of it.

>

> This question is to settle a question between my 15 yr old and me.

> Although he understands that he is at risk for CD/DH, he insists

> that his high school biology teacher told the class that he (my

son)

> cannot transmit actual CD to his own kids because 'genetic diseases

> are only transmitted thru the maternal genes'. Therefore, his

> children will not develop CD, though they may be carriers, and if

he

> has a daughter, her children could have actual CD. I tried to

> explain that I don't believe that's true (ie, Woody Guthrie's kids

> being at risk for Huntington's, therefore, genetic diseases can be

> passed thru paternal genes), but you know that Moms don't know

> anything these days!

The diseases that he is refering to are called X-linked genes and mt

genes. The X chromosome is carry in 2 copies in females and a single

copy in males. Recessive genes (generally loss of function) generally

have no affect on females because they have an alterative copy

expressed in about 1/2 the cells in the body. And instance of X-

linked gene is the hair color genes in the cat, the calico cat for

instance can only be female, and males either have one color or the

other. The patches on a female calico cat represent the expression of

one X-chromosome while the other is turned off. I thought that is

interesting. mitochondrial genes, >95% are inherited from the mother,

a few to no percent from the father. This is because the male sperm

has but a few mitochondria and the egg has bunches of them.

The only positively known genes that are associated with CD are on

the autosomal chromosome #6, these genes can be passed at equal risk

from maternal or paternal lines. The other known risk factors differ

markedly between different groups and are pretty much an unknown. The

recent paper I mentioned in gliadin science makes a passage that most

of the examples of CD they had in thier study (statistically

insignificant based on N) indicate that the father passed the disease

to his offspring)

The X chromosome is an average to large chromosome, humans have 22

other chromosomes, the risk of a factor being passed on X, if that

factor is unknown is between 1:11 and 1:22. mtDNA are 16500

nucleotides in length (compared to 3,000,000,000 for the human

genome) so that there is not a high risk that whatever other factors

you have, that they are passed on X or mtDNA.

As I have pointed out the one way of quelling the issues of familial

CD in family members is to get them DQ typed, if they do not have the

susceptibility type then there is a very low chance they will have a

life threatening disease. The secondary issue about their children,

they can get those children typed at birth and know with certainty

the risk, so they need not even worry about this now if they do not

have the DQ type. There is only a 40% chance they will marry someone

with DQ2.3 or DQ8 and there is only a 50% per child that the child

will aquire the spouses DQ, so that the risk is only 20% per child in

the F2 generation if the son does not have the DQ type, we can

multiply this by the non-DQ associated risk and the risk in the F2 is

considerably lower than the F1 risk, but still higher than the risk

of general population, including DQ2.3 and DQ8 bearers.

IOW don't put the cart before the horse.

Secondarily I don't consider Coeliac Disease a genetic disease, the

DQ types are not diseased DQ types, and while the susceptibility is

inherited, the culprit for CD is the massive artificial selection

that has occurred with grain crops in order to increase their

agrarian properties. Does one blame scherosis on weak liver genes or

or alcohol consumption.

These properties are also the cause of late onset diabetes in most

individuals, and other health related disorders. Sceince might find a

way in the next few years to select for alpha/gamma gliadin producing

crops that do not contain the susceptibility T-cell sites and CD may

disappear in all subsequent generations.

All that is required to do this is to screen wheat for the proteins

that produce these genes, sequence them and find a few mutants that

no longer possess the disease process.

In the meantime I should remind everyone that three continents of

peoples lived 1000s of years without eating wheat, rye or barley and

the food cultures of these peoples have made outstanding

contributions to food culture diversity around the world. So be an

explorer and explore these other food types and enjoy life.

> Can you help settle this question?

>

> Hope you, and all the 'SillyYaks' had a great Holiday Season. This

> was my first 'GF' and although there were some changes in our

> traditional foods and treats (Santa no longer likes White Chocolate

> dipped Oreos, he likes GF gingersnaps) it was still the same

> wonderful holiday.

>

> Blessings to all,

>

> Stormy

[Guest guest]

Philip obviously descibed in a way that is far beyond my abilities,

but if you want it in a practicle example for your son here is one:

My husband has 1 copy of each of the genes (DQ2/DQ8). He has celiac

disease. My daughter has celiac disease, I do not. It was " passed "

from father to daughter and he got a gene from each of his parents.

I hope that helps!

> > Can you help settle this question?

> >

> > Stormy

[Guest guest]

The following indirectly proves that one can get the gene from the mother and the father else how could one person get two DR3/DR3 genes.

"Recent results indicate that individuals who carry the DQA1*0501 and DQB1*02 alleles and in addition have an extra copy of the DQB1*02 allele have an increased risk of developing Celiac Disease. This is called a "gene-dosage effect". The DR types of individuals who usually carry these DQ genes are DR3/DR3 (i.e. DR3 homozygous) and DR3/DR7."

http://www.enabling.org/ia/celiac/cel-hla.html#Q10

I'd go into this deeper with my son. Perhaps a talk with the high school biology teacher with the principal present would be in order. He/she should not be teaching misinformation, or your son needs to know that he doesn't always hear right.

Jo Anne

another genetic question!

I think I'm probably addressing this question to Philip D., who appears to be very well versed in genetics! Thank you for you response to my first question. I must admit that I didn't understand all of the specifics, but I get the jist of it.This question is to settle a question between my 15 yr old and me. Although he understands that he is at risk for CD/DH, he insists that his high school biology teacher told the class that he (my son) cannot transmit actual CD to his own kids because 'genetic diseases are only transmitted thru the maternal genes'. Therefore, his children will not develop CD, though they may be carriers, and if he has a daughter, her children could have actual CD. I tried to explain that I don't believe that's true (ie, Woody Guthrie's kids being at risk for Huntington's, therefore, genetic diseases can be passed thru paternal genes), but you know that Moms don't know anything these days!Can you help settle this question?Hope you, and all the 'SillyYaks' had a great Holiday Season. This was my first 'GF' and although there were some changes in our traditional foods and treats (Santa no longer likes White Chocolate dipped Oreos, he likes GF gingersnaps) it was still the same wonderful holiday.Blessings to all,Stormy