Explain the genetic basis of ABO blood grouping man.

Explanation

Blood differs chemically from person to person . When two different incompatible blood types are mixed ,agglutination (climping together ) of erythrocytes (RBC) occurs . The basis of these chemical differences isdue to the presence of antigens ( surface antigens ) on the membrane of RBC and epithelial cells . Karl Landsteiner discovered two kinds of antigens called antigen .A. and antigen .B. on thesurface of RBC.s of human blood . Based on the presence or absence of these antigens three kinds of blood groups , type ,B. and type .O. (universal donor ) were recognized . The fourth and the rarest blood group .AB. (universal recipient ) was discovered in 1902 by two of Landsteiner.s students Von De Castelle and Sturli .
Bernstein in 1925 discovered that the inheritance of different blood groups in human beings is determined by a number of multiple allelic series . The three autosomal alleles located on chromosome 9 are concerned with the determination of blood group in any person . The gene controlling blood type has been labeled as .L . (after the name of the discoverer , Landsteiner ) or I ( from isoagglutination ) . The I gene exists in three allelic forms `I^(A),I^(B) and I^(O) ,I^(A)` specifies A antigen . `I^(B)` allele determines B antigen and `I^(0)` allele species no antigen . Individuals who posses these antigens in their fluids such as the saliva are called secretors .
Each allele `(I^(A)and I^(B))` produces transferase enzyme . `I^(A)` allele produces N - acetyl galactose transferase and can add N - acetyl galactose to the precursor (i.e H substances ) . In the case of `I^(O)//I^(O)` allele no terminal transferase enzyme is produced and therefore called "null" allele and hence cannot add NAG or galactose to the precursor .
From the phenotypic to each other `(I^(A)=I^(B))` . Their dominance hierarchy can be given as `I^(O)` , but co - dominant to each other `(I^(A)=I^(B))` . Their dominance hierarchy can be given as `(I^(A)=I^(B) gt I^(O))` . A child receives one of three alleles from parent , giving rise to six possible genotypes and four possible blood types (phenotypes ) . The genotypes are `I^(A) I^(A) , I^(A)I^(O) , I^(B)I^(B) , I^(B)I^(O),I^(A)I^(B) and I^(O)I^(O)`