What parental blood groups would you expect for an AB+ child?

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Offline sbkamboh

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i want ur help to find the answer of the following.

"the blood group of a man is O+ and his wife's group is B+, but the group of their child is AB+.
is there any ambiguity about the child's legitimacy? is it possible?
plz reply with logic and solid reason....."

MOD EDIT - please format your subject as a question
« Last Edit: 05/02/2010 11:09:27 by BenV »


Offline Variola

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What parental blood groups would you expect for an AB+ child?
« Reply #1 on: 05/02/2010 23:10:41 »
No ambiguity, the child is Rhesus+, as are both parents so that is as it should be.Blood groups are defined as the type of antigen expressed on the surface of cells.Each child inherits one allele from each parent, A and B are generally more dominant over O.
But to answer your question.... you could have a Mother with A+ and AO alleles and Father with B+ and BO alleles they could have a child with alleles of AB (AB+) AO (A+) BO(B+) or OO (O+).

Hope that helps
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Offline rosy

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What parental blood groups would you expect for an AB+ child?
« Reply #2 on: 07/02/2010 17:36:06 »
Are you sure about that, Variola? You seem to imply that (1) the father is B, which in this example he isn't, and (2) that the Rhesus and A/B/O types are correlated, whereas I think, tho' I'm not sure, that they're not even on the same chromosome...

Blood groups relate to having, or not having, a particular protein expressed on the outside of the cell. For each of the Rh and A/B/O group types, each individual has two alleles, which for the Rhesus type may be + (makes protein) or - (does not make protein). As both parents are Rh+, they may be either ++ or +-.
The child inherits (randomly) one or other of the parents' alleles. If both parents are ++, they will inevitably also be ++, if one is ++ and the other +-, the child may be ++ or +- (50:50 chance). If the parents are both +- the child has a 1:2:1 chance of being ++:+-:--.
The AB grouping is a bit more complicated, in that the parents have two alleles drawn from three types, A (makes A proteins), B (makes B proteins) or O (makes no proteins).
The mother has B type blood, and may therefore have two B or one B and one O antigen, the father has type O blood and therefore is expected to have only type O alleles. So the child would be (naively) expected to have either type B blood (if it inherited a B allele from the mother) or type O blood (if it didn't). So, naively, we might express doubts as to the paternity of the infant.

Sometimes, inheritence even of single genes isn't so straightforward and Mendelian as we might expect, from the genetics we're taught at school. Just as the child inherits one gene in each pair from each of its parent, so the parent inherited one gene from each of their parents (the grandparent generation). The way genetics is taught at highschool level, you'd think that the child would inherit one copy of each chromosome from each parent, and thus would inherit a particular chromosome either just like one of grandma's or like one of grandad's. Infact (except, as I recall for the X/Y chromosomes) the chromosomes swap some material during reproductive cell division, and this occasionally occurs within a particular gene. The example we were taught about in first year undergrad cell biology was that of couples, both deaf due to mutations in the same gene, unexpectedly having a hearing baby because of exactly this type of chromosomal crossover. So basically, genetics is all a bit more complicated that you might think and making assumptions is probably a bad plan...


Offline Spannerman

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What parental blood groups would you expect for an AB+ child?
« Reply #3 on: 15/02/2010 17:04:24 »
The parents blood type may not fully reveal what lies inside their body, each 'grandparent' will have provided one allele which would have built up the gene of the parent, although sometimes hidden a gene may 'skip' a generation so to say but really it is there all along.
School children are often taught genetic flows, this may make it easier for you to understand.

                                         Mom     :       Dad
Parental Phenotype (physical):   B       :        O
Parental Genotype     (genes): B+O     :       O+A -- this A is recessive in the dad and can therefore not be seen

These alleles will cross when making a child, so blood types BO,AO,AB and OO are possible.
This makes a phenotypic ratio (physical outcomes) of 1:1:1:1

Although uncommon the A allele can be recessive leaving the O allele to show as in this case with the dad.