Answer:
D. There is a 25% chance that their child will develop CF.
Step-by-step explanation:
The Delta508 mutation and the R117 mutation are seen in the Cystic Fibrosis (CF) gene. IF a child have both the Delta508 mutation and the R117 mutation, the chances of suffering from CF is high and inevitable.
In this senerio, we can infer that since both parents are heterozygous, the likelihood of developing CF for each child born is 25%
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Here is the complete question
A couple with European ancestry seeks genetic counseling before having children because of a history of cystic fibrosis in the husbands family. ASO testing for CF reveals that the husband is herterozgous for the Delta508 mutation and that the wife is heterozygous for the R117 mutation. You are the couple's genetic counselor. When consulting with you, they express their conviction that they are not at risk for having an affected child because they carry different mutations and cannot have a child who is homozygous for either mutation. What would you say to them.
A. There is a 25% chance that their child will be a carrier of the ∆508 mutation.
B. There is a 25% chance that their child will be a carrier of the R117 mutation.
C. There is a 50% chance that their child will be a carrier of a CF mutation.
D. There is a 25% chance that their child will develop CF.