Forgot your password?
Please enter your username or email address. Instructions for resetting the password will be immediately emailed to you.
Please note: While some information will still be current in a year, other information may already be out of date in three months time. If you are in any doubt, please feel free to ask.
Double heterozygote
- Question
- I am pregnant and did a genetic testing for 95% of the CF mutations. The results were negative for any pathological CF mutation except for the polymorphism c.1408Α>G (homozygote). The father underwent the same testing and two pathological mutations were detected (G576A and R668C) and some non pathological polymorphisms. The genetic center characterized the father as double heterozygote. Is there a chance that the baby will inherit only one mutation from the father? Is there any chance that the baby will inherit both mutations from the father? If yes, will the baby be simply a carrier of two mutations and one healthy gene (from me) and will not be in danger of having CF, or will it have CF due to the two mutations?
- Answer
- Dear friend,
You are pregnant and have been checked for 95% of the CF mutations. The polymorphism c.1490A>G (M470V) was detected in homozygotic state, i.e. it exists in both chromosomes. From a similar testing in the father it was found that he carries the CF mutations G576A & R668C (Pagani et al, 2003, Human Molecular Genetics) as a double heterozygote; it is important that a so-called segregation analysis has been performed to evaluate if both mutations are on the same chromosome. Taking into account the fact that both mutations often occur on the same chromosome, we assume that in the father, both these mutations are on the same chromosome, whereas the other chromosome does not carry any CF mutations.
Given that the embryo inherits one chromosome from you (the mother) and one from the father for all 24 pairs, it follows that:
The baby will certainly carry the polymorphism c.1408A>G, which it will inherit from you (the mother).
There is a 50% chance that the embryo will inherit the chromosome that does not carry any CF mutations from the father. The baby will be healthy and carry as a heterozygote the polymorphism c.1408A>G.
There is a 50% chance that the embryo will inherit the chromosome from the father that carries the two CF mutations. There is not any chance that it will inherit just one. The baby will be healthy and it will carry the polymorphism c.1408A>G in one chromosome and the mutations G576A & R668C in the other.
The possibility of your baby having CF would exist only in the case of you (the mother) having a pathological CF mutation (which you do not).
Dr. Stavros Doudounakis
- 09.04.2013
