If the parents are A+ and Ab+ their children could be as follows:
A+
B+
AB+
A-
B-
AB-
Each blood type carries 2 genes, the AB obviously being AB, the A could either be AA or AO.
So the parents then pass one gene each from those creating the child's blood type.
Then RH factor (+/-) plays in. Again having 2 genes each. A negative person has double negatives always but a positive person can be positive positive or positive negative. Even if you have one gene that is positive and one that is negative you will always be a positive blood type but have a negative gene you could pass on.
So the parents again pass one each of those on to the child.
Even though both of these parents are positive they could be positive negative and each pass the negative gene on and the baby could be negative regardless of the parents being positive.
The same is not true however for two parents that are negative. Since they both have double negatives there is no way for them to have a positive baby.
A+
B+
AB+
A-
B-
AB-
Each blood type carries 2 genes, the AB obviously being AB, the A could either be AA or AO.
So the parents then pass one gene each from those creating the child's blood type.
Then RH factor (+/-) plays in. Again having 2 genes each. A negative person has double negatives always but a positive person can be positive positive or positive negative. Even if you have one gene that is positive and one that is negative you will always be a positive blood type but have a negative gene you could pass on.
So the parents again pass one each of those on to the child.
Even though both of these parents are positive they could be positive negative and each pass the negative gene on and the baby could be negative regardless of the parents being positive.
The same is not true however for two parents that are negative. Since they both have double negatives there is no way for them to have a positive baby.
