If both parents are carriers, there is a 25% chance the child will have BGS, a 50% chance the child will have one mutant copy and be asymptomatic and a 25% chance the child will be asymptomatic and not a carrier.
There is a 25% chance. The child will be asymptomatic a 25% chance. Both parents are carriers. The child will have BGS. The child will have a 25% chance a 25% chance. If both parents are carriers, there is a 25% chance the child will have BGS and a 25% chance the child will not a carrier. BGS is a 50% chance. The child will have one mutant copy. The child will be asymptomatic a 50% chance.