Chromosomal Theory Of Inheritance

The inheritance of blood groups in humans is a classic example studied in genetics. In this case, let's analyze each characteristic option to understand their relevance:

1. Dominance: Some alleles dominate over others in determining phenotype, which is partially observed in blood groups. For instance, the A and B alleles are dominant over the O allele in the ABO blood group system.
2. Co-dominance: This occurs when both alleles at a locus are equally expressed in the phenotype. In the ABO blood group system, the A and B alleles are co-dominant, meaning that an individual with genotype AB will exhibit both A and B antigens on their red blood cells.
3. Multiple Allele: The ABO blood group system is governed by three alleles (A, B, and O) at a single gene locus, making it a situation of multiple alleles. Even though a person can only inherit two alleles, the existence of more than two options characterizes multiple alleles.
4. Incomplete Dominance: This is when the phenotype of the heterozygotes is intermediate between those of the two homozygotes, not applicable to human blood group inheritance.
5. Polygenic Inheritance: Traits controlled by multiple genes; blood groups do not fit into this category as they are determined by alleles at a single locus with multiple alleles.

The characteristics that represent the inheritance of blood groups are:

1. Co-dominance: Both the A and B alleles express themselves equally when present together.
2. Multiple Allele: The presence of more than two alleles (A, B, and O) in the population.
3. Dominance: The A and B alleles are dominant over the O allele.

Therefore, the correct answer is a, b, and c. This choice correctly covers the dominance of alleles, the co-dominance of the A and B alleles, and the presence of multiple alleles.