Q1. Blood groups in the human population are an example of ________.
A Co-dominance Correct
B Incomplete dominance
C Pleiotropy
D Aneuploidy
Explanation
Human blood groups, especially the ABO system, show co-dominance because the IA and IB alleles are both expressed together in the AB blood group. Neither allele masks the other. Incomplete dominance would produce an intermediate phenotype, which is not how A and B antigens behave. Pleiotropy means one gene affects several traits, while aneuploidy is an abnormal chromosome number. The blood-group example is therefore classically used to show co-dominance in human genetics.