13.ABO Blood grouping in humans is an example of: A. Multiple allelism B. Incomplete dominance C. Pleiotropy D. Both a and c
Option A ABO blood grouping in human beings is controlled by three alleles namely IA,IB and IO. These are basically the three alternative forms (alleles) of the gene I. Hence it is an example for multiple allelism. Among the three alleles IA and IB are dominant over IO/i, which is why this case is also an example for dominance. Further, IA and IB are both expressed and therefore are said to be equally dominant (codominant). Hence it is an example of codominance too.
