Paternity question

wijsman at max.u.washington.edu wijsman at max.u.washington.edu
Thu Jul 1 12:58:45 EST 1993


>>If a man has A- blood, what are the blood types his offspring
>>could have (not knowing the mother's blood type)?

>Depending on the mother, his offspring could be A, AB, or O, all + or -.

Don't forget B.  If you don't know the mother's blood group, she could
contribute any of the three alleles A, B, or O.  The father, being A, could
contribute either an A or and O (he could be AA or AO).  Therefore, the 6
possible genotypes in the child, listing paternal allele first, are AA, AB, AO,
OA, OB and OO. In terms of resulting blood types, the 6 genotypes correspond,
respectively, to A, AB, A, A, B and O, or all 4 possible blood types.

Therefore, without knowing the mother's blood type, in this example the
paternal blood type will not exclude the father, no matter what the blood
group of the child is.  If the mother's blood type is known, then if the
mother is A or O, a child who is AB or B will exclude the father.  No other
exclusions are possible with the A father and just one child.

>>To be POSITIVE of who the father of a child is, what would be the
>>next kinds of identification after the blood type?

>"Molecular genetic fingerprinting" (from, say a blood sample) can exclude
>almost all non-fathers.

DNA fingerprinting can also put a very high probability on positive paternity,
but nothing can identify the father with probability 1.0.

Ellen Wijsman
Div of Medical Genetics, RG-25
and Dept of Biostatistics
University of Washington
Seattle, WA   98195
wijsman at u.washington.edu
(206) 543-8987



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