Science Questions

If I have B+ blood and so does my wife how can our son have O+ blood?

Sun, 27th Jul 2008

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Question

Bieran De Saille asked:

If I have B+ blood and so does my wife how can our son have O+ blood?

Answer

Kat -  Well, youíll be asking the milkman what sort of blood group they have! No, this is all very simply explained. Blood group is determined by a set of genes. You get one gene each from your mum and one from your dad. Blood groupís determined by basically two different genes called A or B. You have certain versions of these and you can also get a version called O. These genes make proteins on the surface of your blood cells so if you have a gene that is A you make A proteins and they on the surface of your blood cells. If you have a gene for B that makes B proteins that go on the surface of your blood cells. If you have O then you donít make any proteins. Going back to what I said about you having one gene from your mum, one from gene from your dad  - if you had one B gene and one O gene your blood group would be B because youíve still got  a gene thatís making B proteins. Your blood cells are B. If you then were with someone else who had one B and one O and you had a baby with them your babies could either have BB genes, their blood group would definitely be B; they could be BO because theyíve one gene from you and maybe an O gene from mum or dad or they could have the two Os, in which case they would be blood group O. Itís perfectly possible to have two B parents having an O child from which you can actually infer both of you must be BO.

Chris -  Thatís because group O is recessive.

Kat -  Exactly, group O is recessive because you have no proteins on the surface of your blood cells from this group. If you have even just one A or B gene that determines your blood type.

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Biren Desai asked the Naked Scientists: I have B+ Blood and my wife has also B+ group. But I wonder my son has O positive group, How? What do you think? Biren Desai, Sat, 21st Jun 2008

Don't file for divorce Biren...


http://www.canadiancrc.com/Paternity_determination_blood_type.aspx RD, Sat, 21st Jun 2008

Each of you will have two genes for ABO grouping. O genes don't express a protein, A and B express the A and B proteins respectively.

So if each of you has an O and a B gene, you'll both have B-type blood, but you'll each pass on only one gene (either O or B) to your baby so if both of you happen to hand on the O gene the baby will have O type blood (25 % chance), if one of you passes on an O and one a B gene the baby will have B type blood (50 % chance) or you might both pass on a B gene (25 % chance) the baby will have B type blood. rosy, Sun, 22nd Jun 2008

Hi,

Same case here that Mine & mine wife is having the same blood group B+, and our daughter is having the O+.

I understood here that this could be either B or O, I want to know that whats is approx. probability of B & O globally and also if you can tell what would be for Indian cases.

Regards
Hitendra Bhatia hitendra_bhatia, Sun, 29th Jun 2014

Here is a list of the prevalence of various blood types around the world.

http://en.wikipedia.org/wiki/Blood_type_distribution_by_country

O+ is one of the most common blood types.  B+ a little less so.

As far as your chance of having an O+ child. 

The A, B, and Rh+ genes are essentially dominant. 

If you and your husband are B+, then you could either be:

B/B or B/O  and either Rh+/Rh+ or Rh+/Rh-

Since your child is O+, we know that both you and your husband are B/O.  We don't know which Rh genes you express.

So, if you have another child, then it could be:

BB  (both maternal and paternal B, (B phenotype))
BO  (maternal B, paternal O (still B phenotype)
OB (maternal O, paternal B (B phenotype)
OO (maternal O, paternal O)

So, each of your children has a 75% chance of being B, and a 25% chance of being O.

If either or both parents are Rh+/Rh+, then 100% of your children will be Rh+. 
If you both have Rh+/Rh-, then as above, the child has a 75% chance of being Rh+, and a 25% chance of being Rh-.

If you both have a recessive Rh- gene, and a recessive O gene, then chances of having an O- child will be 1/4 x 1/4 = 1/16 , or 6.25%. CliffordK, Mon, 30th Jun 2014

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