X-inactivation

[nativecoder]

X-inactivation (http://en.wikipedia.org/wiki/X_inactivation) is a process where a gene inactivates one of the two copies of the X chromosome (chosen by random in each cell) (however some genes could remain activated)

 

A) Is anybody using this to inactivate chromosomes as a kind of gene

therapy?

 

B) Taking the case of Haemophilia

(http://en.wikipedia.org/wiki/Haemophilia). You need to have two Xs

chromosomes with the disorder to express the disease. But if we are

inactivating one of the Xs by random in each cell (imagine 50% of

the cells have the good X copy inactivated), shouldn't women carrier

of the disease at least express some symptoms (i.e. a lower blood

plasma clotting factor of the coagulation)? I suppose the process is

more complex than this and having at least 50% of "good cells" masks

any disease symptom.

 

Many thanks!

[Joumana]

you made me carious about your question ...

you said:

(imagine 50% of

the cells have the good X copy inactivated), shouldn't women carrier

of the disease at least express some symptoms

 

The inactive X chromosome does not express the majority of its genes, unlike the active X chromosome

Wikipedia.

 

so there is some expression to some of inactive-X genes

that's why the symptoms of such a disease may appear ..

 

I'm waiting the experts answer ur qeus.s ...

[Mr Skeptic]

I suppose the process is more complex than this and having at least 50% of "good cells" masks any disease symptom.

 

In most cases yes. Genetic diseases tend to be recessive (as dominant ones are very strongly acted on by selection). Alternately, if the gene kills off half the cells, the healthy cells can sometimes take over. Many of these diseases are for chemicals that don't have to be in the cell itself, and are controlled by a feedback loop, so that the healthy cells produce the unhealthy cell's share as well and so keep both alive and healthy.