It all started by someone ask the question, why people have Cystic fibrosis ?

The cystic fibrosis gene have survived through thousands of years around hundreds of human generations most likely because it gives protection against cholera.

A fundamental concept in evolutionary biology is that genes survive through generations only if they offer some advantages to the species.

 

                                 

 How a chronic stable disease can protect from a life threatening disease?  

 Cystic fibrosis is a genetic disease (autosomal recessive ) affect GFTR gene  , in fact it is the most common genetic disease in Europe , it affect the Chloride ion transportation through cell membrane , that will impaired most process depend on Cl movement , for example it make the mucus build up in lungs causing recurrent infection , dray out the Pancreas because it need salt transportation , CF also associated with Diabetes mellitus and infertility .

Maybe you are thinking it is horrible disease and you are right but there is tow type of CF for someone who got the 2 gene defect (affected) , they will have the disease full package with all its complication , it is worse than a diarrhea form cholera per say , in deed it may cause diarrhea by affecting the Pancreas causing malabsorption , it is a disease without a cure , the only thing medicine can do is to control the symptom .
I know a nice brave young girl got the disease but she is a good fighter , her smile never disappear from he face , i admire her and every one fighting it and all mothers of affected children . 

          

If someone have only 1 gene affected (carrier) , that person will have mild or no symptom & because like 50% of his Cl ion channels not working properly he is actually resistant to sever diarrhea from cholera , the last is a bacterial infection release a toxin cause watery diarrhea by manipulating Cl channels and others , it called Heterozygote advantage , when individual have mild or no symptom from a genetic disease with secondary gain  .

                   

Evolutionary biology is changing our view to genetic disease, I meant when we understand a genetic disease like CF as an evolution triggered by special circumstances and aid human survive through time rather than just a gene error , that is quite different . 

The new way of thinking makes it possible for new area of research to understand more the genetic disease with some advantages like Cystic fibrosis and Sickle cell anemia .

I tried to make it short with less complicated medical terminology , i hope it helped , steemit on

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