Question

Which trait is normally controlled by multiple alleles but not multiple genes?

Answer 1

Dominance is a relationship between two alleles of the same gene that affects one allele's phenotype while masking the contribution of the other. A dominant trait is one that is manifested in a phenotype, while a recessive trait is one that is suppressed. Incomplete dominance occurs when one characteristic partially dominates over the other, resulting in an intermediate progeny.

Complete answer:
In humans, the ABO blood group is determined by a single ABO gene, which has three types of alleles (multiple alleles). Codominance is expressed by the ‘a' and ‘b' alleles. Due to the blending of alleles, co-dominance is a sort of dominance in which the offspring are similar to both parents.

Codominance occurs when both parental characteristics are present in the F1 generation. The offspring will have traits from both parents. One of the clearest instances of codominance is the ABO blood type system.

Red blood cells come in a variety of shapes and sizes, including A, B, AB, and O, with or without the Rh component. The difference is in the antigen found on the surface of red blood cells, which identifies an organism's blood type. For example, if a person has blood group A, it signifies that antigen-A is present on the RBC surface.

However, the gene I has the final say. There are three types of alleles in the gene I: IA, IB, and i. The alleles IA and IB create two distinct antigens, but the allele-i produces none. As a result, alleles IA and IB outnumber allele i.

Each diploid organism has two pairs of alleles, as we all know. As a result, there are two sorts of alleles in any given combination in humans. An individual's blood type can be identified based on the mix and dominance of alleles.

Note: An IA and I pair of alleles are present in a person with blood group A. This is due to the allele i's recessive nature, which means no antigen is produced. A individual with both alleles IA and IB, on the other hand, has blood group AB. Because alleles IA and IB are codominant, this is the case. Both genes will create antigens of the same type.