Probability of Bombay Phenotype?

Question

Hello, does anyone know the probability of having a child with Bombay Phenotype from Cis AB father and A type mother?

Answer 1

Requires two parents of type O, both with recessive alleles of the H gene.

No chance whatsoever.

Answer 2

Sorry, but Cattleman is wrong in that one.

Normally (without the H gene in any of its manifestations) we would have the filial generation as AA, A_ , AB or B_ all of which having 25% chance of bearing their respective genotypes as expressed, and 0% of any false phenotype, or Bombay phenotype.

Abnormally (that is, with the presence of an H gene) we would have to consider whether the gene would be recessive “h” or dominant “H”, as well as to which proportions. As for example, I divided the chances for three different scenarios:

1) If there were only dominant H’s in all cases (parents: AB HH + A_ HH), there would be ZERO possibility of a Bombay phenotype.

2) If both parents would take recessive alleles for “h” (AB hh + A_ hh), there would be 100% chance of the kid to manifest a Bombay phenotype, independent of the parents normal ABO blood types.

3) If both parents would have recessive h’s, but only one of the parents would be homozygote (AB Hh + A_ hh, or AB hh + A_ Hh), then the kid would have a 50% chance of acquiring such false phenotype.

The recessive antigen “h” is the “mascarading factor” that inhibits the normal manifestation of A and B antigens. And if there is not antigen, we know that the individual with that trait is seen as a type O, because type O does not have either A or B antigens. Because the antigen “h” can give this false impression (for all that matters the kid could be A, B or AB in fact), common blood analysis based only by the phenotypes ABO can be subject to error, and sometimes fatal ones!

Answer 3

ok, commencing with the easy stuff, a toddler of mothers and dads AB and OO could have the genotype of the two AO or BO, which could supply the phenotype of A or B. So there could be no risk that those mothers and dads have a toddler with the O phenotype. yet it is irrelevent in this question because of the H-locus concern. So for those mothers and dads who're the two heterozygous Hh: Hh x Hh ---> HH, Hh, Hh or hh. If the youngster is hh it could have the O phenotype. regardless of if it is any of the different H-locus phenotypes it rather is going to likely be the two A or B, based which allele it inherited from Dad. the respond is a million in 4.