a) Differentiate between dominance and co-dominance.
b) Explain co-dominance taking an exmaple of human blood groups in the population.

Explanation

a) 1. Dominance- It is condition in which one gene show its effect and the other is marked by it. The gene that express its character is dominant while the other is recessive.
2) Co-dominance- It is a condition in which both the genes are equally dominant and so the character of both genes is well expressed in next generations.
b) ABO blood groups are controlled by gene I. Gene I has three alleles `I^(A), I^(B)` and `I^(0)//i.I^(A)` and `I^(B)` produce RBC surface antigens A and B, respectively, whereas i does not produce any antigen.
`I^(A)` and `I^(B)` are the dominant alleles whereas i is the allele. When `I^(A)` and `I^(B)` are present together, both express equally and produce the surface antigens A and B, as they are co-dominant.