Male Speaker: Cystic Fibrosis. So parents many times, before they get married or after they get married, sometimes have testing done, concerned about certain diseases, one they bring up many times is Cystic Fibrosis. What can a geneticist do to tell the parents they are at great risk or very little risk of developing Cystic Fibrosis.
Michael Marcus: Cystic Fibrosis is a genetic disease which is called autosomal recessive, that is, both parents need to be carriers of the disease in order for them to have a child who has the disease. In fact, even if both parents are carriers, there is still only 25% risk that any child born of those parents will have the disease.
Over the last several years we have been able to identify the gene which causes Cystic Fibrosis. So by looking for the genetic abnormality in the blood stream or in the chromosomes specifically of the each parent, one can sense whether the parents are carriers or not.
The tricky part of that however is that once we have identified the gene, what we have learned is that there are anywhere from 300-500 different mutations of that gene and it's just impossible to test for every different mutation.
So what's done is that they look for the mutations that are most common in those parents who are getting screened. If they find that mutation, it shows that the risk of having Cystic Fibrosis is there, 25%. If they don't find that mutation, it doesn't totally eliminate the risk of Cystic Fibrosis since there is about 15% of the genes that we do not test for, because they are in such a rare occurrence across the spectrum of the population we take care of.
Male Speaker: There is no guarantee but at least gives you a better idea of your greatest risk factors.
Michael Marcus: Correct. So there's not a -- a negative test does not guarantee you don't have Cystic Fibrosis, but it drops the risk significantly. In fact, it drops the risk by 85% over not getting tested at all.
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