Question

How are the ABO blood types inherited? If a child has the phenotype A, what are the possible genotypes he could have? What about a child with type AB? What are the possible genotypes of children born to a mother with type AB and a father with type O?  Write an in-depth paragraph explaining your answer please.

Answer 1

Inheritance pattern of ABO blood group in humans shows dominance,co-dominance and multiple allelism.

Dominance:-The alleles I(A) and I(B) both are dominant over allele i as I(A) and I(B) form antigens A and B ,respectively,but i does not form any anyigen.

Co-dominance:-Both the alleles I(A) and I(B) are co-dominant as both of then are able to express themselves in the presence of each other in blood group AB(IA,IB) by forming antigens A and B.

Multiple allelism:- It is the phenomenon of occurence of a gene in more than two allelic form on the same locus.The ABO blood group in humans are determined by three different allelic forme I(A),I(B) and i.

If a child has a phenotype A ,he could have I(A)I(A),I(A)i as genotype.In first case both the allele has A as surface antigen so it would be expressed as A blood group.In second case one allele has A as surface antigen where i has no antigen and As I(A) is dominant over i It would be expressed as A blood group.

when A child has AB blood group,the genotype he could have I(A)I(B).here inheritance pattern in co-dominace.I(A) has A as surface antigen and I(B) has B as surface antigen.As both are able to express themselves.so,genotype would be I(A)I(B).

The possible genotype of children whose father is having O blood group and mother is having AB blood group would be I(A)i,I(B)i.The children will have A or B blood group.