A baby is born with Type O blood. The mother has type A blood. There is some question
about the baby’s paternity and there are two men that could be the baby’s father. One of them
has Type O blood and the other has Type B blood.
Are either of the men the baby's father?
about the baby’s paternity and there are two men that could be the baby’s father. One of them
has Type O blood and the other has Type B blood.
Are either of the men the baby's father?
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Actually, both of them could be the baby's father, so this is why this test can sometimes rule out paternity but it cannot definitely rule it in. Today, of course, we have more sophisticated DNA tests which are highly accurate.
Let's look at why both of these guys could be the father.
Mom has type A blood, but her baby has type O blood, so she has to be heterozygous (AO) because type O is recessive to both A and B alleles so she must carry a type O gene or her baby would not be type O.
Crossing her with the type O suspect, whose genotype is OO because type O is recessive and requires two alleles for this phenotype, this is what we get:
A O
O AO OO
O AO OO
This paring has a 50-50 chance of having a type O baby, so he could definitely be the father.
Now, let's look at the type B man, and again assume that he is heterozygous and carries a type O gene.
A O
B AB BO
O AO OO
This paring has a 25% chance of having a type O child. The percentage is lower, but it is possible as long as the man is heterozygous and carries a type O gene along with his type B gene, for him to be the father also.
A DNA test would be needed to find out for sure.
Let's look at why both of these guys could be the father.
Mom has type A blood, but her baby has type O blood, so she has to be heterozygous (AO) because type O is recessive to both A and B alleles so she must carry a type O gene or her baby would not be type O.
Crossing her with the type O suspect, whose genotype is OO because type O is recessive and requires two alleles for this phenotype, this is what we get:
A O
O AO OO
O AO OO
This paring has a 50-50 chance of having a type O baby, so he could definitely be the father.
Now, let's look at the type B man, and again assume that he is heterozygous and carries a type O gene.
A O
B AB BO
O AO OO
This paring has a 25% chance of having a type O child. The percentage is lower, but it is possible as long as the man is heterozygous and carries a type O gene along with his type B gene, for him to be the father also.
A DNA test would be needed to find out for sure.
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Both parents could be the baby's father.
For the baby to have type O blood, the mother's genotype must be AO, rather than AA. If her genotype were AA, her child could only have the genotypes AO, AB, or AA, none of which yield the phenotype of type O blood.
If the man with type B blood had the genotype BB, then he is not the father because their children only could have type AB or type B. However, he could have the genotype BO, in which case any child he has with the woman has a 25% chance of being blood type AB, 25% chance of having type A, 25% chance of having type B, and 25% chance of having type O.
A child with the type O blood man and the woman has a 50% chance of having type O and 50% chance of having type A.
Thus, if the genotype of the man with type B is homozygous, the father is the man with blood type O.
If the genotype of the man with type B is heterozygous, the father could be either man.
If anything I explained is unclear, draw a Punnett square.
For the baby to have type O blood, the mother's genotype must be AO, rather than AA. If her genotype were AA, her child could only have the genotypes AO, AB, or AA, none of which yield the phenotype of type O blood.
If the man with type B blood had the genotype BB, then he is not the father because their children only could have type AB or type B. However, he could have the genotype BO, in which case any child he has with the woman has a 25% chance of being blood type AB, 25% chance of having type A, 25% chance of having type B, and 25% chance of having type O.
A child with the type O blood man and the woman has a 50% chance of having type O and 50% chance of having type A.
Thus, if the genotype of the man with type B is homozygous, the father is the man with blood type O.
If the genotype of the man with type B is heterozygous, the father could be either man.
If anything I explained is unclear, draw a Punnett square.
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woah..