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Doctors' Answers to "Frequently Asked Questions" - Blood Type
Gene Testing for Blood Type
Answer: The evidence is not absolute, merely predictive. That is, you can give the odds of the relationship, not absolute proof(unless a peculiar gene shows up).
Answer: Everyone has two different blood type markers with one each inherited from each parent. The most common are A, B, and O, although there are other markers, especially in other parts of the world. A and B are dominant, that is AO or AA is read as A , BO or BB is read as B and AB is read as AB. The only individuals who have O as a marker are OO . So , your mother is AO your father is BO. The son received one O from each and is OO, read as O. The daughter received A from mother, B from father and is AB. The plus marker is also dominant and each parent could be ++ or +- and the children could all be plus if they inherited one plus from either parent.
Answer: There are three blood types. These are A, B, and O. In addition, there
is an additional antigen which marks the cells as either positive(+) or negative(-). In
general, one receivers one set of markers from each parent and O is not expressed. That is
if one parent contributes and A and one parent O. The child will be Type A (actually AO).
If one parent contributes A and the other parent B, the child will be AB. Positive is also
dominant. That is if either parent contributes +, the child will be plus. So, each child
can be either +, -(plus), - , +(plus) +, +(plus) or -, -(negative). Having an antigen will
cause a reaction. So, Type A cannot receive B or AB, but can receive type O. Also,
positive can receive negative without a reaction, but not the other way around. Therefore,
O negative is the universal donor and can be transfused to any blood group. There is a
rare type called O(h), Bombay which has A and B markers, but can't express the antigen due
to an enzyme defect. These patients can only receive blood from another Bombay type-a,
which is a very rare problem. Blood typing is very useful in paternity and identification
testing. You can see that a child with O parents will only be O.
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