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If two persons with $‘AB’$ blood group marry and have sufficiently large number of children, these children could be classified as $‘A’$ blood group: $‘AB’$ blood group : $‘B’$ blood group in $1 : 2 : 1$ ratio. Modern technique of protein electrophoresis reveals presence of both $‘A’$ and $‘B’$ type proteins in $‘AB’$ blood group individuals.This in an example of
partial dominance
complete dominance
codominance
incomplete dominance.
Solution
(c) : The phenomenon of expression of both the alleles in a heterozygote is called codominance. The alleles which do not show dominancerecessive relationship and are able to express themselves independently when present together are called codominant alleles. As a result the heterozygous condition has a phenotype different from either of homozygous genotypes, $e.g.$, alleles for blood group $A\ (I^A)$ and for blood group $B\ (I^B)$ are codominant so that when they come together in an individual, they produce blood group $AB$.
