A RH negative father has a RH negative son. What is the possibility of other children being RH negative? May we then conclude that the son's mother is also negative?
1 Answer
It all depends on the genes carried by the mother. If the mother is double recessive, all children become negative; but in this case, son's mother may not be negative.
Explanation:
Having a positive blood type is determined by the presence of the RHD gene, which encodes for the Rh D Antigen on the surface of Red Blood Cells. If that antigen is not present (due to defective genes), then the person has a negative blood type.
The RDH gene is present in 2 copies in our genes. However, just 1 copy is enough to have the Rh D Antigen and have a positive blood type. And vice versa, you would need to have both 2 copies of the genes to be defective in order to be negative blood typed.
So in this example, the father is
- From this information, we can conclude that the mother has at least 1 defective gene out of her 2 copies. So if the other copy is defective as well, then she would be
#Rh(-)# and hence, all their children will be#Rh(-)# . - However, if the mother's other copy of the RHD gene is NOT defective, then it means she is
#Rh(+)# and hence there is the chance that she might pass on this working gene to their second child, making that new child#Rh(+)# .
This can be summarized by this illustration:
I hope that answers your question.
Further Reading:
