Question

8. What cannot be father's blood group iſ the mother has blood group 'B' and child blood
1
1
group is 'O'?​

Answer 1

Explanation:

I’m not a blood banker (immunochemistry is where I work), but I think I can explain it pretty simply.

A person with type A blood can have a genotype (basically a set of genes for a characteristic such as a blood group) of AO or AA. The O allele (one copy of a gene in a genotype) is present in the AO genotype but will not be expressed in the phenotype (observable characteristic - in this case a blood type). Both AO and AA genotpyes will have type A blood; however the AO genotype can give the O allele to offspring (O represents a lack of the gene alleles for the A or B antigen which gives you type A, B, or AB blood).

The same goes for people with type B blood. They can have a genotype of BO or BB. The O allele is there in the BO genotype, but not expressed. They will have a phenotype of type B blood, but they can give the O allele to offspring.

If an AO parent and a BO parent have a child together, and the child gets the O allele (gene copy) from both of them, then the child will have O blood type. Both alleles in the child must be O for type O to be expressed phenotypically.

AO parent + BO parent = Possibilities of AB (expressed as AB), AO (expressed as A), BO (expressed as B), OO (expressed as O). 25% chance of each

If either parent is AA, BB, or AB then they cannot have a child with type O because they can only contribute an A or B allele to the child. If A or B is present in the child’s genotype it will be expressed (there might be some very rare mutations where something else could occur, but I don’t know of any myself).

GENOTYPE (2 alleles)———————————————PHENOTYPE

AA, AO…………………………………………………………………… Type A blood

BB, BO……………………………………………………………………. Type B blood

AB………………………………………………………………………. Type AB blood

OO………………………………………………………………………… Type O blood

There are some other much rarer types such as the Oh or Bombay blood type, but ABO groups are by far the most commo

Answer 2

The father's blood group cannot be 'AB' if the mother has blood group 'B' and child blood group is 'O'.

• If the mother has a blood group 'B', then the alleles present can be either of the two- $I^{B}I^{B} \:or\:I^{B}i$.
• If the child has the blood group 'O', then the alleles present must be $ii$ as this is a recessive trait.
• So, it is clear that the child has received one $i$ from each of the parents.
• Thus, the father's blood group cannot be $I^{A}I^{B}$ as no $i$ is present here.