Question

ABO blood grouping in human beings cites the example of
A. Incomplete dominance
B. Co-dominance
C. Multiple allelism
D. Both B and C

Answer 1

Hint: Blood type is the classification of blood that can be done by the presence or absence of antibodies and antigenic substances that are inherited. These antigens present on RBCs can be proteins, glycoproteins, carbohydrates depending on different blood types.

Complete answer: ABO blood grouping in human beings cites the example of both codominance and multiple allelism. Codominance occurs when an offspring inherits a pair of an allele that is in the heterozygous form and is fully expressed. As a result, the phenotype of the offspring will be a combination of both the parents. The alleles in codominance are neither dominant nor recessive.
Diploid organisms have two alleles but when these alleles exist in more than two allelic forms it is called multiple allelism. Multiple allelism generally occurs in pairs and the gene occupies a specific location called locus on the chromosome. In ABO blood typing, the gene IB and IA are dominant equally and they always express equally, i.e. they are neither recessive or dominant so, they do not suppress each other functions and they are co-dominant. There are three or more alternative forms for a gene. In the ABO system, the gene will occupy the same locus on the chromosome. So, the ABO system shows multiple allelism.
a) Incomplete dominance: Incomplete dominance is a phenomenon that occurs when a dominant allele or a gene completely masks the recessive allele and the organism's physical appearance will have a mixture of both alleles effect. It is also called partial dominance or semi-dominance. For example in a snapdragon flower, when a red flower is crossed with a white flower, the resulting flower will be pink.
Hence, the correct answer is option D.

Note: In ABO blood groups, Blood group O is also known as the universal donor and the blood group AB is also regarded as the universal acceptor. A significant protein called the Rh factor is a type of protein found on the outside of red blood cells. The protein is genetically inherited (passed down from your parents).