Why is human blood type an example of multiple alleles? codominance?

It is because when alleles show a co-dominant relationship , neither allele is dominant and both are expressed in the phenotype of the heterozygote. The human ABO blood groups provide a good example of codominace. The ABO system is due to a gene that codes for molecules on the surface of red blood cells

Genetic engineering is the answer.

Giga is the second highest prefix on the normal scale, the first is terra.