Blood typing : phenotype Genotype

[Proteinic]

Hi
I’ve a question and I hope to find an answer to it
it is about blood group inheritance
If there are three allele controlling the blood type
Let’s call them A, B, i
A and B are codominant whereas i recessive, If we did a blood typing can we predicate the genotype from just the phenotype ??
Or can we get the allele frequencies from just testing the blood group

[MrMistery]

No, and no.
If the person has AB or O you know his genotype. If he has A or B, then you have no way of knowing for sure.
Allele frequencies can only be figured out by testing a statistically relevant sample of people(a large sample).

[Proteinic]

Thank you MrMistery for the answer
I read a population study (The heterozygsity is predicated ) (done for a sheep breed) done by blood grouping I know there is a codominancy between A and B but what I couldn’t understand how did they know the heterozygosity between A and i
There are other population studies done by blood typing, how did they use the phenotype to get the genotype???????

[Proteinic]

If the genotype cannot be predicted how it is useful to use blood group as a genetic markers ?

[MrMistery]

it's not. In fact it can't be done. Unless they were trying to figure out the gene frequencies, which would be rather easy to calculate using the phenotype frequencies and some basic math...

[F4T32008]

But I think the blood type cases only can be found in the books, and I never heard the blood type (genotype) cases in reality.

But it can be solved using the HW equilibrium
A+B+i=1

[MrMistery]

My point exactly, but the gene frequencies will not give you the genotypes of an A or B individual.