Blood type

If the father is O+ and mother is A+, can there child be B-

[Medlabtech12]

Hello cdc29,
Just reading your question with regards to blood type. If the father is O pos and the the mother is A pos you can NOT produce an offspring that is B neg. Here is why, we will deal with the blood groups and leave out the Rh factor for simplicity (will explain that after).
As parents we each donate half of our genetic make to our children so for example the father is blood group O so he carries 2 gene's OO so he can only donate a O to his off spring but the mother is group A so she could be AO, or AA but nothing else so she could donate either a A or an O to her offspring. So the only possible blood type for there child would be OO= group O or AO= group A. So it is impossible to give birth to a child that has a group B. There are only 6 possible blood types (Rh asside for now).
You can have OO, AO, AA, BO, BB, AB. (Think of the O as being nothing meaning no antigens on the Red blood Cells).

Rh factor is a bit different and they use a big D and a little d to represent the Rh factor so if you have D say from your father and a little d from your mother (your child would be Dd) in which case you would have an Rh factor of being positive where as if you have both little dd's you would be considered Rh negative (this is a recessive trait).

So in closing the only way to have a B neg child is the mother would have had to be an AO (Rh Dd = pos) and the father would have been either a BO, BB, AB (Rh Dd= pos). The mother would pass on an O (Rh-d) and the father would have to pass on a B (Rh-d) to give you the blood type BO (Rh-neg). Any time you have a A or B with an O it is always going to be that letter (A or B group that is dominate as I said previous the O is not having nothing on your Red Blood Cells).

Hope I didn't confuse you to much.

Medlabtech12

[Medlabtech12]

Oh one more thing is if the parent is AB they could donate either a group A or B but that would mean that there blood group would be AB not just group A or group B.

Group O (especially O neg are the universal donators) can donate to anyone because they carry no antigens on the red blood cells.
Where as group AB is the universal acceptor they can have any blood because they have both antigen on the red blood cells and won't have a transfusion reaction.

They give women of child bearing age O neg so that they don't develope a antibody to the Rh factor.

[Dragon1973]

Hello Cdc29,

I have not much further to add (since the above explanation is very specific) except to mention a great site for you to see which has blood type calculator/chart as well as a simple but concise explanation regarding how the outcomes are possible.  The site was constructed to assist with court and paternity questions.

See here:  http://www.canadiancrc.com/Paternity_determination_blood_type.aspx

In short the answer to your question (from the chart I have provided) Generally for a child to have B, with a mother who is A, the father must be B or AB.  (I have not including the negative factor (Rh) - which is explained further down in the chart from the link I provided)

I hope this helps.  Please feel free to message for more details.

In addition to anything I have mentioned, please keep in mind, that while I or others may have extensive knowledge in many areas, you should always seek professional medical advice from your own physician, as it pertains to medical conditions or concerns.

Good luck, and if you have any other questions that I can help you with, please feel free to message me directly.

Sincerely,
Sandi (Dragon1973)
MedHelp Genetics Community Leader;
Children - Special Needs Community Leader;
Down syndrome Community Leader & Ds Group Forum Founder/Moderator;
MTHFR Group Forum Founder/Moderator;
Pregnancy: June 2011 Community Leader