This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics And Genetic Disorders, Subject name: Pediatrics
ABO blood group is an example of? 
Select and explain. 
A. Co-dominance, B. AD, C. AR, D. Mitochondrial inheritance
A: Co-dominance
Answer: A: Co-dominance 
Explanation: a. Co-dominance(Ref: Nelson's 20/e p, Ghai 8/e p 641)Codominance--When both alleles of a gene pair are fully expressed in a heterozygote, e.g. blood group antigens.