Question

ABO blood group system is due to _____ .

Answer 1

Multiple allelism:

1. At a single genetic locus, the presence of more than two alternative contrasting characteristics is regulated by several alleles.
2. There are several alleles for a single gene.
3. All multiple alleles in homologous chromosomes occupy the respective loci.
4. There is only one allele of the group on each chromosome or gamete.
5. Example: ABO blood group system in which three alleles I^A, I^B, and i control the inheritance of blood group in humans.

Final Answer: ABO blood group system is due to multiple allelism.