Multiple Allelic Inheritance of A, B, AB and O Blood Types

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Multiple Allelic Inheritance of A, B, AB and O Blood Types

Multiple Allelic Inheritance of A, B, AB and O Blood Types
Bernstein (1925) proposed that inheritance of A, B, AD and o blood types of man is determined by a series of three allelomorphic genes. The gene controlling blood types has been labeled as I (after the name of immune traits) or L (after the name of discoverer, Landsteiner), The L gene exists in three different allelic forms: L^A, L^B and L^O. The first two alleles produce characteristic antigens on the surface of red blood cells or erythrocytes. Thus L^A allele specifies A antigen, L^B allele B antigen and L^O allele specifies no antigen.
The pedigree analysis has shown that alleles L^A and L^B have dominance over allele L^O. Likewise, the pedigree analysis of A and B parents revealed that children have both A and B antigens and so it was concluded that the alleles L^A and L^B have codominant relationship between them. The dominance hierarchy of this allelic-series can symbolized as L^A=L^B>L^O.

Further studies have shown that the antigen A is heterogeneous and may have four uncommon subgroups as A¹, A², A³, etc. The B antigen also has been reported to contain three variants. The L_A allele thus, may occur in atleast three other allelic forms. viz., L^A₁ L^A₂ and L^A₃. Pedigree analysis have shown that L^A₁ allele is dominant over L^A₂ and L^A₃ alleles; the L^A₂ allele is dominant to L^A₂ allele and L^A₃ allele is recessive to L^A₂ and L^A₁ alleles. Now, the dominance hierarchy L^A=L^B>L^O can be better represented as follows:
[(L^A₁> L^A₂>L^A₃) = L^B] > L^O
The series of multiple alleles of gene 'L' may produce 15 genotypes and 8 phenotypes

Table Phenotypes and genotypes of multiple alleles of gene.

Phenotype	Genotype
A₁	L^A₁ L^A₁, L^A₁ L^A₂, L^A₁ L^A₃ , L^A₁L^O
A₂	L^A₂ L^A₃, L^A₂ L^A₃ , L^A₃L^O
A₃	LA3 LA3 , LA3LO
A₁B	L^A₁L^B
A₂B	L^A₂L^B
A₃B	L^A₃L^B
B	L^B L^B, L^B L^o
O	L^o L^o

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