CBSE Class 12-science Answered
Dominance: The alleles IA and IB are dominant over allele i as IA and IB form antigens A and B, respectively, but i does not form any antigen.
Co-dominance: Both the alleles IA and IB are co-dominant as both of them are able to express themselves in the presence of each other in blood group AB (IAIB) by forming antigens A and B.
Multiple allelism: It is the phenomenon of occurrence of a gene in more than two allelic forms on the same locus. The ABO blood group in humans is determined by three different allelic forms IA, IB and i.
The above three explanations prove that the inheritance of ABO blood group in humans shows dominance, co-dominance and multiple allelism.
Genotype |
Surface antigen |
Blood group |
IAi |
A |
A |
IAIA |
A |
A |
IBi |
B |
B |
IBIB |
B |
B |
IAIB |
AB |
AB |
ii |
- |
O |