CF-gene

Question

I have a half-sister, she has been diagnosed with one CF-gene. As I did not know here up to now, I fear, that my son as nephew resp. half-nephew also carries that gene. Is there a probability for this? My sister and me we have the same father, but not the mother??!!
Thank you

Answer

Dear questioner,

in general your son can only carry the same genetic information (means also the "CF-gene") as his half-aunt, if also you have inherited this gene (the "CF-gene"). As you have only the father in common with your half-sister, your father would have also to be the gene-carrier of the "CF-gene" - in case he is not, your son can not have inherited the "CF-gene" of his half-aunt. In case your father would be genetic carrier of the "CF-gene", you can estimate the probability: For you and your half-sister - concerning the gene of the father - there is a probability of 50% that you carry the same information, with a probability of 50% you became other genetic information compared to your sister.
In case you would also be carrier of the "CF-gene", it is for you and your son: with a probability of 50% you would have given the gene to your son, with a probability of 50% you have transmitted the other "healthy" gene. I assume hereby, that you do not suffer yourself of CF - means that you might carry in maximum one "CF-gene" (we carry two copies for all hederitary factors - one from the father and one from the mother. The illness of CF does only occurr, if both copies are transmitted as "CF-gene").
Yours sincerely,
F. Stanke

02.07.2009