Sometimes,there are more than two alleles for a given chromosome locus. In this case,a trait is said to be governed by:

Progeny with blood group '$O$' cannot be obtained in which of the following crosses?

Which one of the following blood groups is expressed in both homozygous and heterozygous conditions?

$A$ man of blood group-$A$ marries a woman of blood group-$B$. Both of them are heterozygous for their blood group. The chances of their first child having blood group $AB$ will be: (in $, \%$)

What are the products of the $I^A$ and $I^B$ alleles?

$A$ man with blood group $A$ marries a woman having blood group $B$. The maximum possible blood groups among their progenies are